What was going on when I was born?

International Early returns in El Salvador indicated that the moderate Christian Democrats had won more votes than any of the five other parties in Sunday's elections, but the victors' final total would not give them a majority in the new constituent assembly. The extreme right-wing Nationalist Republican Alliance led by Roberto d'Aubuisson, a controversial former army major, was in what the United States Ambassador called a ''strong second position.'' (Page A1, Column 6.) The Administration was jubilant over the apparent victory by Salvadoran moderates. Secretary of State Alexander M. Haig Jr. called the voting ''a victory we have all won.'' (A1:5.)

Five men described as members of the Bonanno crime family were indicted by a Federal grand jury in Manhattan yesterday. The charges against them included conspiracy to murder rival gang members and the attempted robbery of a Manhattan town house owned by the sister of the late Shah of Iran. Six other men said to be members of the Bonanno organization were indicted on similar Federal racketeering charges last November. A Federal Bureau of Investigation official, Richard T. Bretzing, said the 11 indictments had ''severely wounded'' the Bonanno group, which law-enforcement agencies list as one the five major organized crime factions in the New York metropolitan area.

Rescue workers early today abandoned a day-long effort to tunnel to a 48-year-old Scoutmaster wedged inside an old cave here and began digging away the entire hillside housing the cave. Col. Clinton L. Pagano, Superintendent of State Police and one of the leaders of the rescue operation, said destruction of the hillside posed the risk of killing the trapped man, Donald Weltner, if, in fact, he was alive. But Colonel Pagano said the ''quarrying operation,'' as he described it, offered the only possibility of freeing Mr. Weltner. ''We have nothing left, no further options to pursue,'' Colonel Pagano said at 12:05 A.M. today. ''It eliminates the possibility of getting him out of there with a chance of resuscitation.''

The Price of Health Examining the Medical System Third of five articles. By LAWRENCE K. ALTMAN At a time when the cost of medical care is soaring and doctors are being urged to practice more cost-effective medicine, many people are asking these basic questions: How good is American medical care in relation to its cost and what would have to be sacrificed in terms of quality to reduce that cost? The technological sophistication of American medicine is regarded as unsurpassed. The expertise of this nation's doctors in applying it has helped extend the lives of millions of people and has improved the quality of life for millions more. And the gains have occurred concurrently with a huge American investment in health. From 1940 to 1980, the share of the gross national product devoted to health care rose to 9.4 percent from 4 percent.

THEY are all world-famous: 100 young concert pianists, Olympic swimmers, tennis players and research mathematicians who reached the top of their fields between the ages of 17 and 35. But their names are the secret of a research team at the University of Chicago that promised anonymity in order to investigate how these exceptionally talented people got where they are. After completing their analysis of the life histories of these outstanding people, the investigators, headed by Prof. Benjamin S. Bloom, one of the nation's foremost educational researchers, have identified several conditions that stand apart from native gifts and, in nearly every case, appear crucial in producing excellence. ''The old saw that 'genius will out' in spite of circumstances is not supported by our study,'' Professor Bloom said. As the data emerge from the study, they seem to show that most human beings are born with enormous potential - in one area or another - and also demonstrate the extraordinary power of parents.

SMALL buff-colored lumps are mottling the bark of tree trunks and limbs all over the Northeast again this spring, raising the likelihood of another massive infestation of gypsy moths. As the days grow warmer, the lumps will split open, freeing untold billions of caterpillars that will start to do the thing they do best: eat leaves. The devastation wrought by these caterpillars has led to intensive efforts to better understand them and some promising approaches for controlling them, but their spread throughout most of the country is expected to continue for some time. Since its accidental introduction in New England more than 100 years ago, the gypsy moth has slowly spread west and south. But dramatic population explosions caused five million acres of trees to be stripped of their leaves in 1980 and some 13 million acres were defoliated in 1981, levels far surpassing those of previous years. Last year the insect caused visible defoliation of trees in 11 Eastern states, and smaller infestations have recently been found in 19 other states, including California, Washington and Oregon.