Washington ? Fewer teen-agers are smoking cigarettes or using illegal drugs, but a survey released Tuesday shows a troubling increase in the use of inhalants by younger adolescents.

The smoking rate among younger teens is half what it was in the mid-1990s, and drug use by that group is down by one-third, according to the University of Michigan study, done for the National Institute on Drug Abuse. Less dramatic strides have been made among older teens.

Health experts and government officials called the annual survey of eighth-, 10th- and 12th-graders a sign of continued progress in the effort to reduce youth drug use and said further declines would come only with a sustained public education campaign about the consequences of drug abuse.

Overall, illicit drug use among teens declined by 7 percent over the past year, and 17 percent over the last four years. There are now 600,000 fewer teens using drugs than in 2001.

Altogether, gains in 2004 over 2003 were modest. Researchers are troubled by increases — especially among eighth-graders — in the use of inhalants such as glue and aerosols, and a rise in the use of the pain-control narcotic OxyContin. Use of most other drugs declined or held steady.

Health officials said they were concerned that use of inhalants, which are easily accessible to children, might rebound unless children were warned about the grave dangers they pose. Inhalant use had been declining since 1995, when the Partnership for a Drug-Free America began an anti-inhalant media campaign.

“Research has found that even a single session of repeated inhalant abuse can disrupt heart rhythms and cause death from cardiac arrest or lower oxygen levels enough to cause suffocation,” said Nora Volkow, director of the National Institute on Drug Abuse.

Researchers also noted the apparent growing popularity of OxyContin, a powerful and potentially addictive synthetic narcotic. Up to 5 percent of 12th-graders and smaller percentages of younger teens reported having tried it in the last year, the study showed. By contrast, 1 percent or less of teens had tried heroin in a year.

The survey found 15 percent of eighth-graders, 31 percent of 10th-graders and 39 percent of 12th-graders had used drugs in the previous year — down 1 percentage point or less from the year before.

This was the eighth consecutive year that smoking rates among surveyed teens dropped, a turnaround that began in 1996 among students in grades eight and 10 and a year later among 12th-graders.

Researchers credited higher cigarette prices, tighter marketing practices, anti-smoking ads and withdrawal of the Joe Camel logo among reasons smoking has fallen out of favor with more teens. Close to three-quarters of surveyed 12th graders now say they’d rather not date a smoker, up from close to two-thirds in 1977.

“When smoking makes a teen less attractive to the great majority of the opposite sex, as now appears to be the case, one of the long-imagined benefits for adolescent smoking is seriously undercut,” said Lloyd Johnston, lead researcher for the Monitoring the Future study.