This pilot study assessed the safety and efficacy of intravenous anti-D in eight Rh(D)-positive women with immune thrombocytopenic purpura (ITP) during the second and third trimesters of pregnancy. The median pretreatment platelet count was 28 x 109/l. The patients received one to seven anti-D infusions at a mean dose of 62.7 micro g/kg, and the response rate to anti-D was 75%. A haemoglobin decrease of > 2.0 g/dl occurred only once. Fetal hydrops was not identified by ultrasonography. The direct antiglobulin test was positive in three out of seven Rh+ newborns, none of whom was anaemic or jaundiced. Anti-D is effective and appears to be safe for both mother and fetus.