The purpose of this work is to study the possible relationships between Rh and HLA foeto maternal immunizations and to evaluate the clinical implications of HLA antibodies in children with hemolytic disease of the newborn. 74 families including 246 children were investigated. These were divided into 3 groups on the basis of increasing severity of the hemolytic disease. HLA antibodies, with usually well defined specificity, were found in 32,43% of Rh immunized women. This incidence is analogous to that found in Rh non-immunized mothers. HLA immunization did not appear, through the present investigation, to influence the clinical course of the Rh hemolytic disease.