The objective of this study was to determine the exclusive breast-feeding practices, return of menstruation, sexual activity and contraceptive practices among breast-feeding mothers in the first six months of lactation. The study was based in Onitsha, South Eastern Nigeria. A structured questionnaire was used to obtain data from breast-feeding mothers on their age, educational attainment, breast-feeding practices, return of menstruation, sexual activity and contraceptive practices within the first six months of lactation at intervals of 6 weeks, 10 weeks 14 weeks and 6 months post delivery. Analysis of the information obtained showed that out of the 178 mothers who participated in the study 81% of the mothers were within the ages of 20 - 34 years. While all the mothers had formal education, the majority (59%) had secondary education. Seventy-three percent initiated breast-feeding within one hour of delivery. On discharge from hospital, all of them had already established breast-feeding which continued up to six weeks and dropped to 97.8% at six months. Exclusive breast-feeding which was practised by 100% on discharge dropped to 3.9% at six months. The feeding regimen was on demand as practised by 98.9% of the mothers. Menstrual flow had returned in 33.8% of the mothers by 6 weeks of lactation, and had risen to 70.2% at six months. There was more prolonged lactational amenorrheoa in exclusively breast-feeding mothers than in those who were not. By 6 weeks post delivery 31.6% of the mothers had resumed sexual activity and this rose to 93.6% at six months. With the resumption of sexual activity only 5% of the mothers resorted to contraceptive practices other than lactational amenorrhea and this increased to 54% at six months. There was no pregnancy in any of these women during the six months period. While appreciating the role of lactational amenorrhea in child spacing and considering the early return of sexual activity among the mothers the practice of introducing contraceptive practices needs to be encouraged especially in women whose menstruation has returned.