Early geographic relocation has been implicated as an important correlate of psychopathology, learning difficulties, and behavioural problems among child and adolescent populations, yet systematic studies of the potential influence of relocation on youthful drug use have not been conducted. This study explored the relationship between number of geographic moves before the age of 16 and the timing of onset of drug use and progression to drug-related problems. Data were obtained from 3,700 young adults aged 18 to 35 years participating in the 1990-1991 Ontario Mental Health Supplement, a large random probability survey of the residents of the Province of Ontario, Canada. Holding constant potential confounding factors, results showed highly significant positive relationships between moving and early initiation of illicit drugs including marijuana, hallucinogens, crack/cocaine, and illicit use of prescribed drugs. Among marijuana users, moving was also associated with a hastening of time to marijuana-related problems. Relationships between moving and measures of alcohol use/problems (onset of first drink, onset of any alcohol-related problem) were either weak or nonsignificant. Important sex differences were found, with statistically significant relationships between moving and early drug use initiation and progression occurring primarily among males. Future research is required to test for possible mediating mechanisms linking relocation with drug use as well as moderating influences. Efforts should also focus on finding out why drug use appears to be a more common response to relocation among boys.