Failure to complete treatment during alcohol detoxification is a major complication of effective clinical management. We determined the socio-demographic characteristics, the pattern of alcohol and drug use, the hepatitis C status and the psychiatric state of these patients, using retrospective data on 470 first admissions to a specialist alcohol in-patient unit. The 316 patients (67.2%) who had a planned discharge (PD group) were compared with the 154 patients (32.8%) who had unplanned discharges (UPD group). Patients in the UPD group were younger on admission, had higher Alcohol Problems Questionnaire scores, had started to drink heavily at a younger age, were more likely to have previously used cocaine, amphetamines and heroin, and to have smoked cannabis in the 30 days prior to admission. They were more likely to be positive for markers of hepatitis C infection, to have a borderline personality disorder, antisocial personality disorder, or to have concurrent opiate or benzodiazepine dependence. PD was associated with depressive disorder. Early identification can be made of alcohol-dependent individuals at risk of premature drop-out during in-patient treatment. Interventions to retain patients at risk of premature UPD should be developed.