Lysergic Acid Diethylamide (LSD) is a hallucinogenic drug that received considerable attention in the 1960's and early 1970's. It produced a wide variety of psychological phenomena, including a variety of perceptual disturbances which would manifest among some users long after the drug had left the system. These phenomena were commonly referred to as "flashbacks" and may have been largely responsible for the drug falling out of favor among recreational drug users. This report describes histories of LSD use among alcoholism treatment facility inpatients and reports specific characteristics of flashbacks and the degree of subjective distress experienced during flashbacks. Findings indicate a statistically significant relationship between number of doses and incidence of flashbacks.