In many cross-sectional studies an association has been found between snoring and hypertension. However, differing results have been obtained when confounding factors have been taken into account. To establish whether snoring is a risk factor for developing hypertension, a population-based, prospective survey was performed. In 1984 and 1994, 2,668 males, aged 30-69 yrs at baseline, answered questionnaires concerning sleep disturbances and somatic disease. Of the habitual snorers in 1984, 12.5% reported that they had developed hypertension during the period, compared with 7.4% of the remaining subjects (p<0.001). In a multiple logistic regression model persistent snoring, i.e., reported habitual snoring in both 1984 and 1994, was found to be an independent predictor for the development of hypertension among males aged 30-49 yrs (odds ratio 2.6, 95% confidence interval 1.5-4.5) after adjustments for age, body mass index (BMI), weight gain, smoking, alcohol dependence, and physical inactivity. Among the subjects aged 50-69 yrs in 1984, no association between snoring and development of hypertension was found. Although based only on reported data, the results indicate that persistent snoring is an independent risk factor for the development of hypertension among males aged <50 yrs. Prospective surveys, including whole-night sleep recordings, are needed to establish whether this is due to a higher prevalence of obstructive sleep apnoea syndrome among snorers or whether nonapnoeic snorers with increased upper airway resistance also have an increased risk of developing hypertension.