To examine whether medical history and nasopharyngeal examination are useful for predicting obstructive sleep apnea syndrome (OSAS) and to compare these findings with those of the gold standard, polysomnography. Patients underwent polysomnography recordings for 2 nights and an otorhinolaryngologic examination, including flexible endoscopy and the Muller maneuver. Nasal and pharyngeal findings were scored in a semiquantitative way. The medical history of each patient was taken using a standardized questionnaire. Anatomic and functional findings and patient history were correlated with the mean apnea-hypopnea index (AHI). An otorhinolaryngologic clinic. A total of 101 patients presenting with a primary complaint of snoring. Differences between patients with OSAS and primary snorers were assessed using the Mann-Whitney test (anatomic findings), t test (Muller maneuver), and chi(2) test after Pearson correlation (questionnaire). P values less than .05 were considered statistically significant. The mean +/- SD AHI of the patients was 19.7 +/- 21.5); 52 patients had an AHI higher than 10, which confirmed the diagnosis of OSAS. These patients tended to report the occurrence of apneas more frequently than patients with an AHI of 10 or lower. The average ranks (Mann-Whitney findings) of patients with AHIs higher than 10 vs those with AHIs of 10 or lower were 52 vs 50 for septal deviation; 50 vs 52 for tonsil size; 53 vs 49 for low velum level; and 56 vs 46 for hyperplasia of the tongue base. None of these differences reached statistical significance. Mean +/- SD narrowing of the airway during the Müller maneuver was significantly (P<.05) more pronounced in patients with an AHI higher than 10 than in patients with an AHI of 10 or lower at the levels of the velum (80% +/- 20% vs 68% +/- 30%) and the tongue base (57% +/- 24% vs 44% +/- 27%). None of the reported medical history and/or anatomic parameters alone or in combination could be used to distinguish patients with OSAS from snoring patients. Snoring patients, therefore, should be examined at least by a nocturnal screening test for OSAS before any therapeutic decision is made.