Blood-stained maternal milk at delivery and during lactation was prospectively studied in 7774 livebirths over a period of 2 years (1986-1988). Eight mothers had this atypical breast discharge, a prevalence rate of 1:971 livebirths (0.1%). The characteristics of this phenomenon were: early appearance (frequently a short time after delivery), with normal bacteriologic and cytologic investigations, disappearance in 2 to 5 days, without adverse effects on the mothers and their babies, no recurrence after cessation, and occurrence in the previous pregnancies (3 of the 5 multipara). As a result, the best policy is to reassure the parents about the benign and transient course of this condition and to recommend continuation of breast feeding.