What was going on when I was born?

The 67-year-old man had lymphoma, a form of cancer. The disease was tightening its grip, attacking his skin and his lymphatic system. Chemicals and radiation were failing. Then his doctors started a new treatment with substances called monoclonal antibodies designed to seek out his cancer cells exclusively and help kill them. These special antibodies, the most potent biological ''guided missiles'' known to science, were given repeatedly while the doctors watched for signs of dangerous toxicity from the new treatment. There were no such signs. By the end of four weeks the man was looking better and feeling better. Some tumors on his skin disappeared; others became soft and flat, signs that they were being attacked. The patient's fevers and night sweats ceased. A medical report described the response as encouraging.

In their first confrontation of the Democratic mayoral primary campaign, Mayor Koch and Assemblyman Frank J. Barbaro disagreed heatedly yesterday about whether the Mayor had saved the city from fiscal insolvency and whether the city should grant tax abatements to real estate developers. ''He did not save the city from bankruptcy,'' Mr. Barbaro asserted several times during a televised exchange in which all three Democratic mayoral candidates appeared. The Brooklyn Assemblyman also accused the Mayor of giving ''$700 million to real-estate people and then taking thousands from them in contributions.'' Recalls Warning by Rohatyn The Mayor quoted a warning made in January 1978 - just after he took office - by Felix G. Rohatyn, then and now the chairman of the Municipal Assistance Corporation, that the city still faced a perilous fiscal situation.

An article in Metropolitan Report on Friday incorrectly described the pub- lic schedule this summer of Senator Harrison A. Williams Jr., Democrat of New Jersey. Senator Williams has been making speeches, attending pub- lic functions in his district and per- forming various constituent services.

The New York City school system, under court order to accommodate handicapped children of all kinds, is grappling with one of the most complex challenges it has faced. It must confront long waiting lists, a shortage of qualified teachers and resistance from superintendents, principals and others who would prefer to devote their limited resources to those who are not handicapped. As the school term that begins Sept. 10 approaches, the school system has a waiting list of 12,684 children who are by law entitled to special programs but either have not been evaluated or have not been placed. Others have been placed in the wrong kinds of classes or not integrated in classrooms with children who have no handicaps, as mandated by Federal law.

Chase Manhattan announced it was abandoning its 40 percent interest bonus for investors who sign up early for the new ''All Savers'' certificate program. The development came after an unusual warning by the Internal Revenue Service over the weekend that the bonuses might not allow savers certain tax deductions. (Page A1.)

''She is a shipwreck full of astonishments.'' - Peter Gimbel, who helped organize the exploration of the Andrea Doria. (A10:2.)

The Mets, who live by small things, wasted a number of large things yesterday in Shea Stadium and paid the price by losing, 6-3, to the Cincinnati Reds. Mostly, the Mets wasted scoring opportunities, which they had frequently, and spent the afternoon chasing the Reds. Then, when Dave Collins and Ken Griffey tagged Dan Boitano for consecutive home runs in the sixth inning, the chase was over. As a result, the Reds took the series, two games to one, and the Mets headed for Houston with their second-half revival cooling a bit. Craig Swan, their leading pitcher, and Joel Youngblood, their leading hitter, were left home to treat their injuries; Tom Hausman was recovering from elbow surgery, and the pitching staff was still being manned mostly by rookies.

Since late April, even during the leisurely days of the baseball strike, Rudy May had watched the video cassettes of his dismal pitching performances over and over. He had carried the tapes from his house in New Jersey to his home in California and back again, speeding up the replays, slowing them down and trying to figure why he had not won a game since April 29. Today, after months of tinkering with his mechanical problems, conferring with his coach and trying to keep his spirits up, he finally ended his losing streak with a complete-game 5-1 victory over the White Sox. It was the Yankees' third impressive victory in a row here, leading Manager Gene Michael to speculate that his team might be starting a long winning streak.

Most Americans will see their new tax cuts eaten up by increased costs of natural gas if President Reagan decides to speed up decontrol, a consumer group charged today. The group, Energy Action, said in a study of the impact of decontrol that a four-member family with an annual income of $20,000 would pay $1,063 less on taxes in the next three years, but would spend $1,080 in increased bills for natural gas under the decontrol plan recommended to Mr. Reagan. ''If the President, who promised a new prosperity and economic recovery, accomplishes natural gas decontrol, most Americans will face a new poverty and economic regression,'' charged Edwin Rothschild, director of Energy Action.

The five radar surveillance and battlecontrol aircraft that the Reagan Administration proposes to sell to Saudi Arabia will not have the same key technological systems as United States Air Force models, according to a Defense Department document, The systems to be omitted from the Saudi planes are designed to resist enemy jamming of radar and communications and to help manage a large-scale aerial battle. However, according to the document, the Saudi Airborne Warning and Control System planes, known as Awacs, ''will be identical to the standard U.S. Air Force'' version of the planes. The question of how the Saudi Awacs will be equipped is likely to be important during hearings and debate in Congress, which can veto the sale in a vote expected to come in October. The Defense Department document was part of the formal notification of the proposed sale that was sent to Congress last week. Officials said the Saudi version of the aircraft would be a highly capable early-warning, surveillance and battle-control plane, particularly in the military environment around the Persian Gulf oilfields in eastern Saudi Arabia.

After showing some improvement this spring, service on the city's subway system declined in June and July, setting summer failure records, according to Transit Authority statistics. The problems on the subways reflected poor performance in the entire transit system run by the Metropolitan Transportation Authority, according to one analysis of the figures released yesterday. The system also takes in buses and commuter railroads. According to a separate study, service on the IRT Division - already regarded as the most troubled in the subway system - was even worse last month than it was in the dead of winter.

In a move that could set a precedent for other banks and thrift institutions and materially affect investment decisions by individuals, the Chase Manhattan Bank yesterday announced that it was abandoning its much-publicized 40 percent interest bonus for investors who sign up early for the Government's new ''All Savers'' certificate program. The certificate program is scheduled to go into effect Oct.1. The move by the nation's third-largest bank came after a warning by the Internal Revenue Service on Saturday that it had ''substantial doubt'' that the tax-free savings incentives contained in the new tax law would apply to the high-interest investment packages that banks had been offering. An I.R.S. spokesman said yesterday that a definitive ruling would be made ''shortly.''