We analyzed a total 498 individual interviews carried out with 71 groups for the support of breastfeeding (Grupo de Incentivo ao Aleitamento Materno - GIAMA). Interviews were performed from January 1989 to December 1990 on the first postnatal appointment to study the causes of weaning at the Dr Sylvio Henrique Braune health center, in the city of Nova Friburgo, state of Rio de Janeiro. The prevalence of exclusive breastfeeding in the first month of life was 49.6%, and the most frequent cause of weaning (77.9%) was that "breastfeeding was not enough to feed the infant." The cry of babies was an important factor, since 68.6% of mothers claimed that breastfeeding was not enough to feed the infant, based on their crying. One of the goals of the GIAMA is to provide information for and support breastfeeding mothers in order to deal with the real causes that make babies cry and to prevent early weaning.