Every weekend, thousands of young people-from teens to those in their 20s-attend Southern California underground raves like this one, all-night dance parties where nitrous oxide-laughing gas-is often peddled openly in $5 balloons in a carnival-like atmosphere.

The scene is a transplant from England's rave phenomenon, which is fueled by the will to party nonstop outside the purview of authorities. Lawlessness, in fact, is a common theme found at local rave parties: They move from spot to spot every weekend to evade police and create the anarchic atmosphere that attracts not only laughing gas peddlers, but dealers of $20-plus capsules and "disco biscuits" laced with a designer drug called ecstasy.

Criminal penalties for sale or use of MDMA are similar to those for laughing gas. And like its warehouse party cousin, no records are kept for ecstasy arrests. The Los Angeles district attorney's office reported no ecstasy prosecutions last year, and only two ecstasy labs were seized nationwide in 1990, according to the U.S. Department of Justice.