Three primigravidas developed Rh sensitization after unexplained third-trimester fetal death. One patient manifested sensitization after the diagnosis of fetal death had been made but before delivery occurred. The other two demonstrated anti-D antibodies early in the next pregnancy, despite having received postpartum Rh immunoglobulin. Unsensitized Rh-negative women with unexplained third-trimester fetal death should be screened routinely for fetomaternal hemorrhage when fetal death is discovered, so that adequate prophylaxis against Rh sensitization can be given.