['We assessed penile rigidity during sleep and the relationship of sleep abnormalities with priapism in adults with sickle cell disease.', 'This was a case-control study of 18 patients with sickle cell disease and a history of priapism during the previous year, and 16 controls with sickle cell disease. Participants underwent overnight polysomnography and RigiScan® Plus recording to detect penile rigidity oscillations.', 'The priapism group (cases) showed a higher apnea-hypopnea index and oxyhemoglobin desaturation parameters than controls. A lower positive correlation between the apnea-hypopnea index and oxyhemoglobin desaturation time was observed in cases than in controls (Spearman coefficient ρ = 0.49, p = 0.05 vs ρ = 0.76, p <0.01), suggesting that desaturation events occurred independently of apnea. Two controls and 14 cases had a total sleep time that was greater than 10% with oxyhemoglobin saturation less than 90% but without CO(2) retention. Penile rigidity events were observed during rapid eye movement sleep and during stage 2 of nonrapid eye movement sleep, particularly in cases. The duration of penile rigidity events concomitant to respiratory events was higher in cases than in controls. Regression analysis revealed that the periodic limb movement and desaturation indexes were associated with priapism after adjusting for rapid eye movement sleep and lung involvement. Finally, oxyhemoglobin saturation less than 90% was associated with priapism after adjusting for lung involvement, hyperhemolysis and the apnea-hypopnea index.'] Is priapism associated with sleep hypoxemia in sickle cell disease?