Estimates of Ecstasy users in the country range from 500,000 to three million.

Ms. Pirro said that in the county, the police have seen Ecstasy users becoming suppliers.

Ecstasy users experience generalized difficulties with prospective memory.

The postcards were distributed to thousands of teenagers and implied that Ecstasy users had shrunken brains with holes in them.

But like all drug researchers, he said it was impossible to find heavy Ecstasy users who used no other drugs.

His papers, he said, always warn that poor performance by heavy Ecstasy users may have been caused by other drugs.

The report, in the current issue of Neurology, was based on a study of 15 Ecstasy users, ages 17 to 31, over a yearlong period.

Over the course of the year, for example, the Ecstasy users' ability to recall the passages after a delay declined by about half.

Ecstasy users are a different group entirely.

Far from reducing harm, its advocates promote policies that lead to increased usage rates and a false sense of security for Ecstasy users.