The aim of the study was to assess prevalence and treatment modalities of insomnia in general practice. To investigate the course of insomnia, a longitudinal study design was adopted. Two thousand five hundred and twelve patients (age 18-65 years) were investigated with a questionnaire in general practice (T1). Four months later (T2) and again 2 years later (T3) a questionnaire was sent to all patients who had complained about severe insomnia at the time of the first inquiry. To assess insomnia, operationalized diagnostic criteria were applied (DSM-III-R). Eighteen point seven percent suffered from severe, 12.2% suffered from moderate and 15% suffered from mild insomnia. In the course of 2 years insomnia appeared as a chronic health problem. A high comorbidity of severe insomnia was found with chronic somatic and psychiatric disorders, especially with depression. Of the severely insomniac patients, 23.9% used prescribed hypnotics habitually, mainly benzodiazepines. The use of prescribed hypnotics remained rather stable during the whole study period. More than half of the patients reported a daily use of the hypnotics for 1-5 years or longer, but only 22% of the severely insomniac patients reported at the time of the third inquiry a significant improvement of insomnia due to the administration of sleeping pills. Thus, the long-term administration of benzodiazepine hypnotics seems to be an inadequate treatment strategy in chronic insomnia. Whether the occurrence of rebound insomnia after benzodiazepine withdrawal may be one of the main factors for chronic hypnotic use requires discussion.(ABSTRACT TRUNCATED AT 250 WORDS)