Conventional polysomnography (CPS) is a complex, costly procedure that is not widely available, meaning that it is difficult to apply it in patients suspected of having obstructive sleep apnea syndrome (OSAS). Various procedures have therefore been proposed for screening candidates for CPS. We studied the usefulness of visual analysis of nocturnal oximetry in 96 patients suspected of having OSAS. The OSAS diagnosis was confirmed by CPS in 67 (69.8%). Oximetry was positive in 70 cases. Sixty-one patients were positive by both oximetry and CPS, while 9 and positive oximetry results and a negative CPS. We conclude that nocturnal oximetry has a 91% sensitivity and 69% specificity for OSAS, with a positive predictive value of 87% and a negative predictive value of 77%. We believe that nocturnal oximetry may be a useful way of screening for OSAS, in order to decrease the number of CPS performed on patients without the disease.