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 II (p<0.0001). Among patients (n=196), follicular T levels (p=0.910); E2 (p=0.088) and E2/T (p=0.180) did not have significant associations with age. However, a significant decrease in the intrafollicular level of androstenedione was noted with an increase in the age of women (Spearman R= –0.320; p<0.01). Serum AMH level decreased with increasing age (Spearman R= –0.372; p=0.002), while the level of E2 remained within the physiological values (p=0.3). An increase in the activity of ovarian aromatase with an increase in the age of women was found (p<0.0001), however, this relationship was not observed among patients with PCOS (p=0.208). Conclusion. The activity of ovarian aromatase increases with increasing age of patients and helps to maintain the level of E2 within physiological values for reproductive age, which probably has an adaptive value. The absence of a connection between the activity of ovarian aromatase in patients with PCOS and age may indicate a violation of this adaptive mechanism.