This study investigated factors leading to premature discharge from the residential substance abuse treatment programme at the University Hospital of the West Indies (UHWI). Two hundred and twenty-four patients, mean age 36 +/- 9.75 and age range of 16-66 years were studied The patients, 87.5% men, were admitted to the programme over the period July 1999 to June 2002. Sources of data, including a routine patient-monitoring form and patients' medical records, were reviewed. Data analysis, performed using the Statistical Package for Social Sciences (SPSS), included frequencies, cross-tabulations and analyses of variance (ANOYA). Crack cocaine was the drug of impact for 60% of patients, alcohol for 17% and marijuana for 8%. Treatment ended prematurely for 22.8% of persons whose reasons for leaving included signing out against medical advice or self-discharge (27.4%), absconding (19.6%), fighting (9.8%), drug use (5.9%) and other rule breaking, including sexual acting out (15.7%). Premature discharge was uninfluenced by gender, age, marital status, schooling, employment status or geographical location. There were significantly more premature discharges in persons admitted primarily for crack dependence versus those admitted primarily for alcoholism (p < 0.05). There were also significantly more premature discharges in persons with 0-10 years of using their most problematic substance when compared with 21-30 years of use (p < 0.05) but not when compared with 11-20 years or over 30 years of use (p > 0.05). The influence of duration of substance use requires further elucidation.