The substances did not improve the participants' strength, their physical performance, or certain other measures of health.

"I don't think there's any case for administering these" to elderly people, said Dr. K. Sreekumaran Nair of the Mayo Clinic, lead author of the study, published in Thursday's New England Journal of Medicine.

DHEA, a steroid that is a precursor to the sex hormones testosterone and estrogen, is made by the body, but levels decline rapidly after age 25. DHEA supplements are marketed as rejuvenating agents, and U.S. sales hit $50 million last year.

Testosterone is available by prescription only. But the Food and Drug Administration classifies DHEA as a supplement, meaning it can be sold without meeting the same safety and effectiveness standards as a drug.

Some athletes use DHEA and testosterone to try to boost performance, often in violation of athletic association rules.

The NFL and other professional sports have banned DHEA. Cycling officials have moved to strip the Tour de France title from winner Floyd Landis, after a French laboratory found elevated testosterone levels in his urine.

Apart from this type of use, scientists have wondered if the substances might help older people. Studies with rodents offered tantalizing results that showed DHEA seemed to decrease fat and fight diabetes and heart disease.

But there have been few rigorous scientific studies in humans. A French study of DHEA in 280 elderly people, reported in 2000, found the only benefit was an increase in female libido. A Dutch study this year found no benefit of DHEA in 100 men 70 and older.

The new study was done by researchers at the Mayo Clinic in Minnesota and the University of Padua in Italy.

Over two years, the researchers studied 57 women and 87 men, all of them at least 60 years old. The women were given standard daily doses of DHEA or identical fake pills. The men were given real or fake DHEA, as well as a testosterone skin patch or a placebo patch.

Blood samples were taken every three months. Participants also were examined for any changes in body fat, hormone levels, bone density, and performance on treadmill, weightlifting and leg flexibility tests. The men and women also filled out questionnaires about how they felt and their quality of life.

Although DHEA and testosterone levels increased in the men and women who took the real treatments, there was no effect on physical performance, quality of life or the body's ability to lower levels of blood sugar.

The testosterone treatments led to a small but significant increase in the amount of body weight free of fat, but that did not correspond to any improvements in strength. DHEA had no such effects.

DHEA appeared to improve density in bones in the arm and neck, but not in the back and hip, Nair said. "That shows an inconsistent or minor effect," he said.

No harmful side effects were detected. That is good news, but it does not mean the supplements are altogether safe, said Simon Yeung, manager of the Web site on supplements and integrative medicine at the Memorial Sloan-Kettering Cancer Center in New York.

In the study, testosterone was given in low doses. Higher levels might have more benefit, but doctors worry testosterone may also raise the risk of prostate cancer, Yeung said. As for DHEA, cancer specialists worry it may increase certain patients' risks of breast and prostate cancer, he said.

Dr. Paul Stewart of England's University of Birmingham said in an accompanying editorial that more research should be done on DHEA, and if it proves safe and effective, it should be regulated as a drug.

"Without a reversal of the current U.S. legislation, DHEA is likely to continue to be used inappropriately, and quackery will prevail," Stewart wrote.

Andrew Shao of the Council for Responsible Nutrition, a supplement trade organization, said DHEA should not be regulated as a drug because people do not use it to treat a specific illness.

A pharmaceutical designation does not guarantee safety, added Shao, referring to Vioxx and other FDA-approved drugs that had to pulled from the market.