Twenty years ago there was a resurgence in the abuse of LSD, a hallucinogen that first became popular in the late 1960’s. This odorless and colorless drug, also known as acid, has a high potential for abuse. While its primary effect is to give users a dramatic change in their visual perception, it also can result in extreme changes in mood, a distorted view of objects, sounds, touch and their own body image. Their ability to make sound judgments is also impaired, and the likelihood of experiencing extreme anxiety and depression is greatly increased. Hallucinogens, from LSD to PCP to Ecstasy, continue to be dangerous and illegal drugs of concern today.