The purpose of this study was to investigate the prevalence, primary causes, and management of insomnia newly admitted patients in a university hospital. Subjects consisted of 168 adult patients (95 men and 73 women, 88 medical and 94 surgical patients) newly admitted to Gyeongsang National University Hospital from September 7 through September 27, 1996. Sleep patterns of all subjects in the usual nights before admission(UN), the previous night to admission(PN), the night on admission(ON), and the 5th night after admission(5N) were investigated using the Korean version of the St. Mary s Hospital Sleep Questionaire. In addition, all insomnia patients and their doctors and nurses in charge were interviewed by psychiatric residents. Additionally, their medical records were reviewed. Prevalence of insomnia were 22.6% in the UN, 42.9% in PN, 51.8% in ON, and 43.5% in 5N. The prevalence of insomnia was significantly increased immediately before and after admission. There were no significant differences in the prevalence of insomnia by age and sex. The most ammon primary causes of insomnia were somatic symptoms and psychological factors in PN, somatic symptoms and noise in ON and 5n. Only 17 (10.1%) of insomnia patients took medicstions for insomnia control(analgesics in 15, hypnotics in 2). These results shorred that the prevalence of insomnia was significantly increased on hospitalization due to somatic symptoms, environmental factors, and psychological factors, but nearly none were adequately managed.