Blood samples from 24 Rh(D) immunized women were analyzed for antibody titers and quantification of anti-D. The HLA-DR and -DQ polymorphisms were identified as RFLP. In 11 women with titers 16-256 the HLA-DQB1 allele *0201 was found in 18%, i e as in a reference population. In 13 women with titers > or = 512 the HLA-DQB1 allele *0201 was found in 85% indicating a correlation between severe Rh(D) immunization with high titers/quantification values and the DQB1 allele *0201. In this group the fetus was severely affected by the immunization and treatment during pregnancy was frequently needed. HLA phenotyping of women known to have anti-D antibodies early in pregnancy seems to be an effective way to assess the probability of severe hemolytic disease of the newborn.