The vertical transmission of HIV (Human Immunodeficiency Virus) has become the main target of prophylactic Zidovudina (AZT) therapy during gestation, parturition as well as for the newborn. To characterize the clinical and laboratory evolution of HIV exposed children. Prospective study of 64 HIV exposed children, classified into two groups. Group A, made up of 23 pairs of mothers and newborns, who did not receive AZT; Group B, made up of 41 pairs, who received AZT at some stage of prophylaxis. The average maternal age was 26.8 years, the use of illicit drugs occurred in 17.2% of the pregnant women, twenty (31.3%) of the women had diseases. Between the groups there were no significant differences related to prenatal frequency of maternal illnesses, birth body dimensions and growth sequence. Both study groups presented with similar lymphocyte and blood counts. On the average, seroreversion took place at 16 months. Vertical transmission occurred in 6 children (9.3%), none of the children in the subgroup who received prophylaxis during all phases were infected. The prophylactic therapy with AZT during all the periods recommended and the long term follow-up of the HIV exposed children constitute one of the best strategies for prevention of the acquired immunodeficiency syndrome (AIDS) in infants.