Currently, the relationship between the sleep and erectile function (EF) is not in doubt; therefore, evaluation of this relationship in the context of sleep medicine (somnology) is the most informative diagnostic method. The article presents the results of polysomnography with the option of simultaneous monitoring of spontaneous episodes of nocturnal erections in 51 men aged 46-55 years without complaints of violation of the EF. The main group (n = 37) consisted of patients with obstructive sleep apnea syndrome (OSAS). The violation of pattern (quantitative and qualitative characteristics) of nocturnal episodes of spontaneous erections in this group of men was revealed, which was regarded as the initial (pre-clinical) manifestation of erectile dysfunction. Thus, modern diagnostic capabilities of sleep medicine allow to effectively evaluate the EF in patients with OSAS and timely assign pathogenetically justified therapy.