People with snoring, excessive daytime somnolence, and nocturnal breath cessation are very likely to have sleep apnea, particularly if they are obese or hypertensive. We collected epidemiologic data to determine the frequency of these findings in an unselected adult population. Respondents in a random digit dialing telephone survey included 685 people (356 women and 329 men, with a mean age of 50 years). Snoring was reported by 37%, gasping by 8%, excessive daytime somnolence by 36%, and hypertension by 28%; all symptoms were more prevalent in respondents older than 50 years. Snoring and gasping were more common in men than in women. Six persons (1%) had all four risk factors, plus a body mass index of one standard deviation above the mean. Eleven respondents (2%) had all four risk factors, but lower weight. We conclude that all risk factors for sleep apnea are more prevalent in persons over the age of 50 years, and that the incidence of sleep apnea in the general population may be 1%.