The aim of this study is to analyze psychiatric comorbidity of alcohol dependence with respect to prevalence rates, time of onset and indications for the course of alcoholism. 100 hospitalized alcohol-dependent patients were investigated. They were diagnosed according to the criteria of ICD-10 assessed by the Composite International Diagnostic Interview (CIDI). In 54% of the patients, at least one additional psychiatric disorder was diagnosed (lifetime). The current prevalence rates for all diagnoses were 49% (1 year) and 38% (2 weeks), respectively. In 71.2% the onset of comorbidity disorders preceded the onset of alcoholism by more than 1 year. In patients with secondary depressive disorders, alcohol-related problems had manifested significantly earlier than in primary depressive patients, but no differences were found in the maximum amount of drinking, the age of onset of excessive drinking and the amount of drinking during the year before the present study. ICD-10 comorbidity rates on the basis of the CIDI are in agreement with former DSM-III-R results based on the DIS. Psychiatric comorbidity seems to play a role in the early stages of alcoholism but not in the later course.