Three different regimens of giving additional fluid to breast fed babies in the immediate Puerperium were monitored in a group of 79 mothers and babies on three different postnatal wards in one hospital. Mean daily intake (± SE) of additional fluids varied widely between the wards; 48 ± 8ml in ward A, 107 ± 14 mls in ward B and 80 ± 13 mls in ward C. There was however no significant interward difference in the duration of breast feeding following discharge home. Increased duration of breast feeding was significantly related to an increased frequency of breast feeds in the first 3 days postpartum, and to the social class of the mother; women in social classes I and II had a high success rate regardless of the ward policy of administration of supplementary fluids. Incidence of neonatal jaundice was not different between the three wards. While this study provides no evidence that witholding extra fluids increases the success of breast feeding, there is certainly no evidence that giving extra fluids is advantageous. There was some evidence that more frequent suckling was associated with increased duration of breast feeding. It would seem appropriate to advocate policies which encourage suckling; the routine use of extra fluids for breast fed babies may be contrary to this objective.