The mortality risk associated with different sleeping patterns was assessed by use of the 1965 Human Population Laboratory survey of a random sample of 6928 adults in Alameda County, CA and a subsequent 9-year mortality follow-up. The analysis indicates that mortality rates from ischemic heart disease, cancer, stroke, and all causes combined were lowest for individuals sleeping 7 or 8 h per night. Men sleeping 6 h or less or 9 h or more had 1.7 times the total age-adjusted death rate of men sleeping 7 or 8 h per night. The comparable relative risk for women was 1.6. The association between sleeping patterns and all causes of mortality was found to be independent of self-reported trouble sleeping and self-reported physical health status at the time of the 1965 survey. Simultaneous adjustment for age, sex, race, socioeconomic status, physical health status, smoking history, physical inactivity, alcohol consumption, weight status, use of health services, social networks, and life satisfaction reduced the relative mortality risk associated with sleeping patterns to 1.3 (p less than or equal to 0.04).