The average length of postpartum amenorrhea reported by breast-feeding women in rural Bangladesh in 1975 was 18 to 20 months. Its duration was found to be only slightly related to maternal nutritional status. There was no evidence of a threshold of weight for height necessary for the resumption of menses postpartum. Factors related to the duration of postpartum amenorrhea were maternal age, socioeconomic status, and supplemental feeding of the infant.