What was going on when I was born?

The Speaker of the House asked the Foreign Relations Committee today to investigate whether the Administration had violated the War Powers Act by not reporting to Congress on recent activities by American military personnel in El Salvador. Speaker Thomas P. O'Neill Jr. made his request in the aftermath of reports that American pilots have been flying reconnaissance missions in support of Salvadoran troops. In addition, Senator Jim Sasser, a Tennessee Democrat, told the Senate Thursday that American military advisers based in the region have been fired upon three times in recent months.

The United States announced today that it was imposing stringent restrictions on the sale to Iraq of five chemical compounds that can be used in making the poison gases Iraq has been accused of using in its war with Iran. At the same time, the State Department confirmed a report in The New York Times today that quoted American intelligence officials as saying they had evidence that Iraq had used nerve gas against Iran. Earlier the United States said it was convinced that Iraq had also used mustard gas, a blistering agent. John Hughes, the State Department spokesman, said the curbs on the export of the chemicals also applied to Iran, but there have been no allegations that Iran has used chemical weapons in the war, which began in September 1980.

Government negotiators and Argentina's 11-bank commercial advisory group tonight reached an 11th-hour agreement on a $500 million package to help Argentina make long-overdue interest payments to the banks. The unusual agreement, announced by the Treasury Department at 11:15 P.M., will provide Argentina with short-term financing from three countries, Mexico, Brazil and Venezuela, which have their own serious debt problems. Under the terms of the financing package, Mexico and Venezuela will each contribute $100 million, while Brazil and Colombia will each contribute $50 million. In addition, the 11 commercial banks, which are Argentina's major creditors and make up the international advisory committee, will contribute a total of $100 million.

People removed from the welfare rolls in 1981 have generally increased their work efforts and their earnings but have not earned enough to make up for the loss of welfare and food stamp benefits, the General Accounting Office said today. Thus, it said, many of the people removed from the welfare rolls were living in poverty. The study by the accounting office, an investigative arm of Congress, was the most systematic and detailed analysis of how welfare recipients were affected by the Omnibus Budget Reconciliation Act of 1981. That law was the vehicle for most of President Reagan's social policy initiatives. The study, which was done at the request of the House Ways and Means Committee, said the law had achieved two of its main purposes: to save money and to reduce welfare caseloads. It also confirmed the Administration's contention that people would not quit jobs to regain eligibility for welfare.

President Reagan today formally ended the United States participation in the international force in Lebanon. The President's action freed United States marines aboard Sixth Fleet ships off Lebanon for duties elsewhere in the Mediterranean. Administration officials said the number of United States warships off Lebanon had already been reduced from about 25 to 15 in recent days. The officials indicated that the battleship New Jersey and the aircraft carrier John F. Kennedy were no longer close to Lebanon.

A panel of administrative judges of the Public Service Commission recommended yesterday that the cost of a call from most pay telephones in New York State be increased to 25 cents from 10 cents. The P.S.C. has rejected such a judicial recommendation three times, but staff members of the P.S.C., which regulates phone rates, and New York Telephone, which operates 90 percent of the telephones in the state, said they expected the increase to be approved this time. The minimum cost for pay calls has been 10 cents for 30 years.

Scientists yesterday reported the development of a new vaccine that promises longer and substantially better immunity to influenza and may reduce the likelihood of major flu epidemics. In tests, all volunteers who received a full dose of vaccine were protected against the illness, which in epidemic years can strike millions of people. The new experimental vaccine, given by nose drops rather than by injection, was made from live viruses modified in a laboratory rather than from inactivated viruses used in conventional flu vaccines. Injection Is Slower Route Medical scientists believe that a live influenza-virus vaccine introduced into the body through the nose produces a better immunity than is possible with a killed-virus vaccine, which must be given by injection.

Paul Castellano, the reputed head of the Gambino organized-crime family, and 20 other people were charged in Manhattan yesterday with operating a group that committed 25 murders and scores of other crimes. The charges were contained in a 51- count Federal indictment, which described the 68-year-old Mr. Castellano as the boss of a crew that had participated in a ''pattern of racketeering activity'' since 1973. The racketeering charges included extortion, theft, prostitution and drug trafficking, as well as the murders. The group committed murders to obtain money and to get rid of witnesses and competitors, according to the indictment. It said six members of the group had not been named as defendants because they had been murdered.

After more than a month and a half in which it has deployed everything in its antisubmarine arsenal in a vain effort to capture apparent underwater intruders around a top-secret naval base, Swedish military officials remain mystified but convinced that the search should continue. ''We have tried and tried to explain the evidence by natural phenomenon but in the end there are reports that can't be accounted for that way,'' said Col. Jan-Aake Berg, the chief spokesman for Sweden's Supreme Commander, Lennart Ljung. The search operation - only the latest of its kind by Sweden - began Feb. 10 after a magnetic detection line was tripped in one of the channels approaching Karlskrona, a base in the south of the country. Two thousand Swedish troops have repeatedly searched islands where mysterious figures thought to be frogmen were reported. The hunt has involved checks of passing vehicles, which in one case included opening a coffin in a funeral cortege.

A Reagan Administration report to be given to Congress concludes that a ban on specific antisatellite weapons may be possible to verify but that Administration experts have yet to figure out how to do it and doubt that it can be done, officials said today. The report, in response to a Congressional mandate to study the feasibility of antisatellite arms control, is to be presented Saturday. It has been several months in preparation, and the final draft was completed only Thursday after what officials described as bitter struggles. State Department officials said they wanted to show Congress that the Administration was trying to study seriously the feasibility of controlling antisatellite weapons, while Pentagon officials made it clear they wanted to close the door entirely on a treaty because of what they said were formidable problems in verifying such agreements.

Following is the text of a letter today from the President to the Speaker of the House of Representatives and the President pro tem of the Senate on the end of American participation in the multinational force in Lebanon: Since the date of my last report to you on the participation of United States armed forces in the multinational force (M.N.F.) in Lebanon, I have decided that the U.S. will terminate its participation in the M.N.F. In accordance with my desire that Congress be kept informed on these matters, and consistent with Section 4 of the Multinational Force in Lebanon Resolution, I am hereby providing a final report on our participation in the M.N.F. U.S. foreign policy interests in Lebanon have not changed and remain as stated in my last report to Congress on Feb. 13. The U.S. is committed to the goals of the restoration of a sovereign, independent and united Lebanon, the withdrawal of all foreign forces and the security of Israel's northern border. However, the continuation of our participation in the M.N.F. is no longer a necessary or appropriate means of achieving these goals. We have discussed our decision with the Government of Lebanon and the other M.N.F. participants, and the other M.N.F. countries have made similar decisions.

Shimon Peres was left as the unchallenged head of the opposition Labor Party today as two potential rivals announced their decisions not to compete for the leadership. The two are former President Yitzhak Navon and former Prime Minister Yitzhak Rabin. Mr. Navon, who was widely regarded as having the best chance of leading the party to victory in the July elections, said at a news conference that he had tested the waters and found party unity the main concern of his colleagues. He said he was afraid a fight would leave the party divided at election time.