Cocaine, marijuana and alcohol have been losing popularity among high school students for almost a decade, but a growing number of young people are using LSD, the drug that virtually defined the counterculture of the 1960s.
"We thought it had largely faded away," said Robert C. Bonner, the head of the federal Drug Enforcement Administration. "But we're seeing an increase in use of the drug now, a re-emergence."
Although the dangers of cocaine and even of alcohol have been firmly established and are hammered at in national advertising campaigns, the full effects of LSD are still a subject of dispute among experts.
They agree, however, that it is not addicting and that it is not used with the frequency of such drugs as cocaine and heroin. The low cost, a few dollars for an experience that can last half a day, adds to the allure.
But several recent cases of violence involving LSD users demonstrate some of the risks. Another danger sign is a rise in the number of people admitted to hospital emergency rooms because of bad experiences with the drug.
Experts say, though, that it is not clear whether LSD should bear the full blame or whether the drug merely sets off fundamentally unstable people.
In some ways, the LSD scene in America today resembles the time of the 1960s flower children.
Now, as then, it is mostly white, privileged and somewhat alienated people who are drawn to the drug. In high schools and colleges around the country, a new generation of students, some wearing their hair long and favoring funky clothes and others who do not stand out from their peers, has begun experimenting with the drug.
Drug experts say hundreds of thousands of other LSD users, many of whom used the drug in the '60s, are now in their 40s and 50s and working as lawyers, journalists, computer scientists, college professors and other professionals.
In addition to the increase in the number of people being treated in hospital emergency rooms, arrests for selling the drug are up sharply and a national survey suggests an increase in LSD use among high school seniors.
But the numbers are still low in comparison with other drugs.
According to the survey, by the University of Michigan, 5.4 percent of the nation's 2.7 million high school seniors said last year that they used LSD in the highest level in seven years and an increase over the 4.9 percent who said so in 1989.
By contrast, alcohol use among seniors declined to 80.6 percent from 82.7 percent, marijuana use declined to 27.0 percent from 29.6 percent, and cocaine use declined to 5.3 percent from 6.5 percent.
The survey, of about 15,000 students each year, has a margin of sampling error of plus or minus one percentage point.
In addition, Steven Hager, the editor in chief of High Times, TC national magazine that chronicles the drug culture and who rarely finds himself in agreement with the DEA, said that he had noted "a big resurgence of interest in psychedelic substances," not only LSD, but certain mushrooms, peyote and mescaline.
Federal drug officials say LSD use peaked in the '70s and then wentinto decline, but never completely went away.
LSD, which takes its name from the initials of the German name for lysergic acid diethylamide, is very different from cocaine, which is astimulant, and heroin, which is a depressant.
LSD, which is derived from a fungus that grows on rye and other grains, does not have a single, consistent effect, experts say, but it amplifies whatever is occurring in the mind, producing a number of often colorful hallucinations and distortions in perception.
Experts warn that taking the drug can lead to panic attacks and flashbacks of terrifying hallucinations.