An American Army population of 36,000 in which hashish was commonly smoked was studied over a three-year period. Direct medical and psychiatric observations of 720 hashish smokers revealed that the casual smoking of less than 10 to 12 gm of hashish monthly resulted in no ostensible adverse effects other than minor respiratory ailments. Panic reactions, toxic psychosis, and schizophrenic reactions were infrequent occurrences except when hashish was simultaneously consumed with alcohol or other psychoactive drugs. Highdose hashish abuse of over 50 gm per month in 110 patients was associated with a chronic intoxicated state characterized by apathy, dullness, and lethargy with mild-to-severe impairment of judgment, concentration, and memory. Severe hashish abuse and its simultaneous use with alcohol or other psychoactive drugs by large numbers of young American men is alarming.