Snoring and sleeping apnea are reportedly associated with morbidity. We used home monitoring (MESAM IV) to measure snoring and sleep apnea in 294 men aged 40 to 65 yr from the volunteer register of the Busselton (Australia) Health Survey. In this group, 81% snored for more than 10% of the night and 22% for more than half the night; 26% had a respiratory disturbance index (RDI) > or = 5, and 10% had an RDI > or = 10. There was a relatively low correlation between percentage of night spent snoring and RDI (rho = 0.47, p < 0.005). Subjective daytime sleepiness plus RDI > or = 5 occurred in a minimum of 3%. Obesity was related to snoring, RDI, and minimum SaO2 (all p < 0.0001). There was no relationship between age and either RDI or snoring, but increased age was related to minimum SaO2 < 85% (p < 0.05). Alcohol consumption was not related to sleep-disordered breathing. Smokers snored for a greater percentage of the night than nonsmokers (41 versus 31%, p = 0.01). We conclude that, in middle-aged men, both snoring and sleep apnea are extremely common, and in this age range both are associated with obesity but not with age. However, a high percentage of snoring is not essential for the occurrence of sleep apnea, nor does it necessarily indicate that apnea is present.