In the anemic environment that prevailed on Wall Street in 1990, medical and drug stocks proved to be the best prescription for financial health.

At the same time, shares of bank and savings and loan holding companies dominated the market's sick list as the year drew to a close.Most broad-based indicators of stock-price trends showed double-digit percentage losses for 1990 as of late December, turning in their poorest performances since the bear market of 1981-82.

Just 11 of 82 stock groups tracked by Dow Jones & Co.'s industry-group indexes posted gains for the year through the close of trading on Dec. 21.

Among the gainers, the medical and biotechnology group led the pack with an advance of better than 20 percent, followed by medical supplies, pharmaceutical manufacturers, health-care providers and retail drug chains.

The performance of these stocks testifies that health care remains a booming, though by no means trouble-free, business in the early 1990s.

While the nation debates what to do about soaring health costs and uneven distribution of medical services, many companies in the field continue to thrive as the population ages and seeks longer, healthier lives.

Technology and other innovation add an extra measure of opportunity, however risky in business terms, for venturesome health-care enterprises both large and small.

A just-published quarterly report by the Value Line Investment Survey on the medical supplies industry cites "growing demand for health care, a decent pricing environment, and the entry of more high-margined products" as major reasons for recent enthusiasm over stocks of this kind.

Even the gloomy outlook for the economy has worked in favor of health-care stocks, by encouraging investors to look for "defensive" issues that are insulated from the effects of a business slump.

As Value Line observed in its latest evaluation of the drug stocks, "pharmaceutical manufacturers have always been known for their defensive characteristics."

"They look particularly recession-resistant this time around, due to the elimination of many low-margined non-health-care product lines over the course of the last several years."

A standout example of a winning health-care stock in 1990: U.S. Surgical, producer of a line of products used in surgical stapling, which soared from 241/8 in January to a recent high just under 70.

Turn U.S. Surgical's stock chart upside down, and you would have a pretty fair representation of what happened to many bank and savings and loan issues over the past year.

Dow Jones's S&L index fell nearly 60 percent; its gauge of money-center banks dropped 37 percent, and its composite of regional banks from the various corners of the country lost 40 percent.

The story gets even more somber when you look at the behavior of many individual issues from the banking and S&L sector - for example, Bank of New England, which fell from above 9 to less than 1, for a drop of about 93 percent.

First City Bancorp, Crossland Savings, Unionfed Financial, Citytrust Bancorp and HomeFed all suffered declines of more than 80 percent.

In the last few weeks of 1990, many depressed financial issues have rallied a bit on buy orders from investors attracted by distress merchandise.

If the upswing in bank stocks were to continue, analysts say, it might start shaping up as a signal that the worst of the nation's spell of debt retrenchment and credit crunch were past.

But whether any such hopes are warranted now remains to be determined in 1991.