The Authors have studied the effects of different surgical interventions on some factors of humoral and cell-mediated immuno-competence: 112 premenopausal women, operated on mainly for benign conditions, have been considered in order to evaluate the influence of various phases of menstrual cycle on surgical immunosuppression. Two schemes were used to stratify the study sample: in the first analysis, we have subdivided the patients in 59 cases in perimenstrual phase (0 through 6 and 21 through 36 days from last menstrual period, LMP) and 53 in periovulatory (7-20 days from LMP). The second stratification relied on the hormone-dependent phases determined by the putative time of ovulation 14 days after LMP: 51 cases in follicular phase and 61 cases in luteal phase have been considered. Immune parameters have been evaluated before surgery and the day after intervention. The first comparison stresses the worst outcome of immune parameters in patients operated on in the perimenstrual period (CD4, activated lymphocytes and C3 have significantly reduced post-operatively). The second part of the study shows no significant difference in the two groups as to such parametres.