To clarify the association of Japanese doctors’sleep habits with working environments and lifestyle, a survey was performed using a self-administered questionnaire in February 2002, targeting a population of 2,455 Asahikawa Medical University alumni. A total of 881 subjects completed questionnaires,yielding a response rate of 35.9%. The mean ±SD sleep duration on workdays was 410.4±60.5 minutes, approximately 30 minutes shorter than that of the general Japanese population. The prevalence of subjective insufficient sleep（SIS）on workdays was 64.5%, significantly higher than that in the general Japanese population. The estimated overall prevalences of various sleep problems are as follows : difficulty initiating sleep, 14.7% ; difficulty maintaining sleep, 15.3% ; poor perceived quality of sleep, 15.6% ; waking without feeling refreshed（WWFR）,30.0% ; and excessive daytime sleepiness（EDS）, 30.8%. SIS had a significant positive association with WWFR and EDS. Doctors’sleeplessness differed depending on their working style. The prevalence of SIS among doctors working at hospitals and clinics with inpatient wards was significantly higher than that among those working in environments without inpatient wards. The prevalence of SIS was significantly associated with the number of working hours,fatigue,and an irregular lifestyle. Habitual exercise did not appear to affect SIS. A multiple logistic regression model revealed that working in hospitals, long working hours（more than 9 hours a day）, fatigue, and an irregular lifestyle were independently associated with SIS［OR＝2.19（95% CI＝1.29-3.70）; OR＝1.95（95% CI＝1.37-2.77）; OR＝1.93（95% CI＝1.38-2.69）; OR＝3.27（95% CI＝2.21-4.84）］. Sleep duration on holidays was approximately 60 minutes longer than that on workdays,and the prevalence of SIS decreased to 32.3%. These results demonstrate that the prevalence of SIS is higher among doctors working at hospitals and clinics with inpatient wards, who tend to have long working hours and irregular lifestyles.