The authors have evaluated the influence of some obstetric events (type and duration of labour and method of delivery) and some pharmacological factors (oxytocic drugs during labour, local infiltration, duration of general anaesthesia, oxytocic drugs and/or ergot derivatives during puerperium) on frequency of breast-feeding at the time of discharge from hospital. About 57% of 356 newborns were breast-fed (wholly or prevalently) at discharge from the "A. Gemelli" University Hospital in Rome, during two months period (march-april 1981). The results showed that all those conditions requiring medical and paramedical action, either instrumental or pharmacological (such as: induced labour, prolonged labour, operative delivery either vaginal or abdominal, particularly in emergency; use of local infiltration; use of oxytocic drugs during labour, particularly for induction; prolonged general anaesthesia in caesarean section) may have an unfavorable effect, nearly always significant, on breast-feeding. According with these results, the Authors suggest the following measures for breast-feeding promotional programme: modification of neonatal routine care to promote an earlier mother-infant interaction during lying-in; limitation of avoidable obstetric procedures and of drugs giving to mothers; a better understanding of pharmacokinetics, both in mothers (placentar passage of drugs and through milk) and in newborns during labour, delivery and puerperium.