This study evaluated the phagocytic activities of neutrophilic leukocytes in both sexes during reproductive age and in women in different phases of the menstrual cycle and in pregnancy. In this study, 9 male and 12 femalemedical students, 17 to 20 years of age, 23 pregnant women and 9 women after delivery were evaluated. Heparinized blood was incubated with heat killed bacteriaStaphylococcus aureus at 37 degrees C for 20 minutes. The bloodfilms were stained with Leishman stain and the phagocytic index was found out by the number of neutrophilic leukocytes ingested with organisms in 100 cells and the total number of organisms counted therein. At the interval of 14 days, on 3 consecutive occasions, the phagocytic index was studied on the same male and female subject. The phagocytic activities of neutrophilic leukocytes were found slightly higher in females than in males; more so in pregnancy than in non-pregnant women, woman controls and after delivery. During the expected ovulation period, the phagocytic activities were observed more than during the menstrual and premenstrual phases. The phagocytic activities were found more in pregnancy and during the ovulatory period in women.