OBJECTIVES Snoring increases with increasing age and body mass, and repeated periods of hypoxia cause nocturnal polyuria. Accordingly, we examined the occurrence of snoring problems in patients scheduled for transurethral prostatic resection. METHODS Of 171 men scheduled for TUR-P, 41 were excluded due to cardiac disease, diabetes, or prostatic malignancy. Of the remaining 130 patients, 12% were troubled by snoring that disturbed their sleep. The severity of their snoring was evaluated by questionnaires, micturition charts, and determination of nocturnal capillary oxygen saturation (SaO(2)) and pulse rate. Plasma levels of cortisol, arginine vasopressin (AVP), and atrial natriuretic peptide (ANP) were measured in the morning and at 2 p.m. Fifteen non-snoring patients also scheduled for TUR-P served as controls. RESULTS Compared to controls, the snoring patients had a significantly higher body mass index (BMI), voided more frequently, and produced more urine at night. They also had a significantly larger number of hypoxic episodes at night, which, along with low SaO(2) levels, correlated with the nocturnal diuresis. Snorers did not differ significantly from controls in regard to excretion of cortisol and AVP, but they did have higher plasma levels of ANP. CONCLUSIONS We recommend that elderly obese men with urgency at night be questioned about snoring, and that micturition frequency and volume charts be completed before deciding to operate.