The existence and function of the let-down reflex was studied in 103 mothers who fed their babies at the breast while in hospital after delivery. Successful breast feeders reported a significantly higher incidence of symptoms of let-down than unsuccessful breast feeders. Successful breast feeders made a significantly higher proportion of their milk available to the baby and the breast pump before let-down was artificially induced with Pitocin. The let-down reflex functioned more erratically in the unsuccessful breast feeders. Methods by which the let-down reflex might be helped to function more adequately are discussed.