In this study, we evaluated the gender differences in body mass index (BMI), age and their effects on apnea-hypopnea index during total sleep time (AHITST) in the Turkish population who were diagnosed with obstructive sleep apnea syndrome (OSAS) and compared them with data from the literature. A computerized database of 244 Turkish patients (194 males, 50 females) who had undergone overnight polysomnography (PSG) and diagnosed with OSAS at BayIndIr Hospital sleep laboratory between October 2004 and January 2007 was reviewed. The male:female ratio of the patients was 3.88:1. Male patients were significantly younger compared to females (48.87 ± 10.82 vs 52.94 ± 12.14 years, respectively, P = 0.003). The BMI and AHITST were similar in male and female patients (BMI = 29.52 ± 4.63 vs 31.17 ± 6.08 kg/m2, respectively, P = 0.083) (AHITST = 27.45 ± 22.97 vs 24.77 ± 23.83, respectively, P = 0.149). For the male and female groups, AHITST increased as BMI increased (P = 0.03, 0.04). The median values of AHITST in male group, for the normal, overweight and obese + pathological obese groups were 12.45, 20.20 and 23.50, respectively, whereas the median values of AHITST in female group were 11.10, 10.95 and 26.20, respectively. In the normal and obese + pathological obese groups, there was no statistically significant difference according to gender, whereas in the overweight group, male patients had significantly higher AHITST (P = 0.02). There was no statistically significant difference between the male and female patients regarding the severity of OSAS (P = 0.358). However, there was a male tendency to moderate and severe OSAS in the normal and overweight BMI groups. In Turkish patients with OSAS, there was no gender difference in BMI and AHITST and female patients were significantly older than the males. The OSAS was diagnosed in men nearly four times more often than in women. © 2007 Springer-Verlag.