Hypothesis/Aims of study. currently, the frequency of suboptimal response (4-9 retrieved oocytes) to controlled ovarian stimulation (cOs) in woman is quite high; however, its efficacy is poorly studied. The aim of this study was to evaluate the main characteristics of iVF / icsi programs in patients with a suboptimal response to cOs. Study design, materials and methods. We performed a retrospective study of 412 iVF / icsi cycles in women with a suboptimal response to cOs, including a comparative analysis of clinical and embryological parameters, ovarian reserve and the efficacy of iVF / icsi protocols. Results. clinical pregnancy rate in ovarian stimulation cycles with a suboptimal response to cOs was 27.9%. The efficacy of assisted reproductive technology (arT) programs in women with uterine fibroids was significantly lower than in patients without fibroids (19.1% vs. 30.5%, p = 0.03; Or = 0.54; 95% ci: 0.31-0.95). clinical pregnancy rate in patients with male factor infertility was significantly higher than in women with anovulation (37.1% vs. 20.9%, р = 0.005; Or = 2.24; 95% ci: 1.27-3.94) or tubal factor infertility (37.1% vs. 24.8%, р = 0.02; Or = 1.79; 95% ci: 1.09-2.94). There were significant correlations between the number of retrieved oocytes with serum anti-Müllerian hormone (aMh) concentration (r = 0.32, p < 0.001) and antral follicle count (aFc) (r = 0.38, p < 0.001). in addition, the need for follicle-stimulating hormone (Fsh) preparations during cOs correlated significantly with ovarian reserve parameters (aMh and aFc) (r = –0.45 and –0.44, both p < 0.001, respectively) and the age of patients (r = 0.47; p < 0.001). Conclusion. The clinical pregnancy rate in women with a suboptimal response to cOs was low. concomitant uterine fibroids represented an additional factor of negative influence on iVF / icsi outcomes in women with a suboptimal response to cOs. The male factor of infertility in patients with a suboptimal response did not reduce the efficacy of arT programs. Ovarian reserve parameters in women with a suboptimal response correlated with the need for Fsh preparations during cOs and the number of retrieved oocytes.