Nearly 1500 women with live births from February through September 1974 were included in this multiple phase study of breast-feeding patterns in a rural area of Banglandesh. The median duration of breast feeding was observed to be 30 months. Over 75% of the women whose most recently born children were living were breast feeding at 2 1/2 years postpartum. The major reason for discontinuing breast feeding in the 1st year was infant death, and in the 2nd year, pregnancy. Insufficient milk was given as a reason for discontinuing breast feeding by 18% of the women who stopped breast feeding for reasons other than child death; among these women almost 60% were pregnant at the time they stopped. Of the breast-feeding women who became pregnant, over 50% continued to breast feed through the 6th month of pregnancy. A sample of 200 breast-feeding women with children ages 17 to 25 months were followed longitudinally for 1 1/2 years or until the mothers conceived. A seasonal trend in suckling time was observed with women reducing suckling during the harvest season. Total suckling time was inversely associated with socioeconomic factors and with infant nutritional status. No association was found between mean suckling time and maternal nutritional status, maternal morbidity, infant morbidity, or child's sex.