The aim - of the study was to compare the activity of ovarian aromatase in patients of different ages with non-endocrine factors of infertility and PCOS in IVF protocols. Material and methods. A prospective cohort comparative study included 196 patients aged 25 to 41 years (32 (28-34)). Women with PCOS were included in group I (n=64), group II included patients with other infertility factors and normal ovarian reserve (n=132). Ovarian aromatase activity was calculated by the ratio of Estradiol (E2)/AMH levels determined on day 2 of the menstrual cycle. Upon retrieval oocytes, a follicular fluid was taken with the determination of E2, testosterone (T), the ratio of E2/T and Androstenedione in it. Results. Intrafollicular concentrations of T (Me=17 vs 18 nmol/l; p=0.303); E2 (Me=2 834 000 vs 2 139 200 pmol/l; p=0.143); E2/T (p=0.088) and Androstenedione (Me=25 vs 18 nmol/l; p=0.083) did not differ among the groups. Ovarian aromatase activity in patients with PCOS was statistically significantly lower than group