Eight heavy snorers underwent nocturnal polygraphic recordings. The principal results are the following: 1. Snoring is an inspiratory (or primarily inspiratory) noise linked to subobstruction of the upper airways. It appears with falling asleep (stage 1) and intensified progressively through the deepening of slow sleep; in REM sleep it becomes discontinuous and is comparable to stage 2 snowing in intensity. 2. In heavy snorers, obstructive apneas are always present and particularly abundant during light sleep (state 2) and REM sleep. 3. In heavy snorers during sleep the systemic arterial pressure reaches and remains at levels higher than those of wakefulness instead of diminishing normally. 4. Some degree of alveolar hypoventilation is associated with snoring when the apneas are especially abundant. These findings confirm the existence of significant polygraphic analogies between snoring and hypersomnia with periodic apneas and indicate that snoring may represent the first phase in the development of this syndrome. Moreover, the effects of snoring on alveolar ventilation and the systemic pressure during sleep suggest that heavy, constant snoring has physio-pathological implications for the cardio-circulatory apparatus.