The prevalence and related clinical features of obstructive sleep apnea-hypopnea (OSAH) in the general population were estimated in a two-phase cross-sectional study. The first phase, completed by 2,148 subjects (76.9%), included a home survey, blood pressure, and a portable respiratory recording, whereas in the second, subjects with suspected OSAH (n = 442) and a subgroup of those with normal results (n = 305) were invited to undergo polysomnography (555 accepted). Habitual snoring was found in 35% of the population and breathing pauses in 6%. Both features occurred more frequently in men, showed a trend to increase with age, and were significantly associated with OSAH. Daytime hypersomnolence occurred in 18% of the subjects and was not associated with OSAH. An apnea-hypopnea index (AHI) > or = 10 was found in 19% of men and 15% of women. The prevalence of OSAH (AHI > or = 5) increased with age in both sexes, with an odds ratio (OR) of 2.2 for each 10-yr increase. AHI was associated with hypertension after adjusting for age, sex, body mass index, neck circumference, alcohol use, and smoking habit. This study adds evidence for a link between OSAH and hypertension.