BACKGROUND: Despite limited data, international guidelines recommend the use of intravenous immunoglobulin (IVIg) in neonates with rhesus hemolytic disease. OBJECTIVE: We tested whether prophylactic use of IVIg reduces the need for exchange transfusions in neonates with rhesus hemolytic disease. DESIGN AND SETTING: We performed a randomized, double-blind, placebo-controlled trial in neonates with rhesus hemolytic disease. After stratification for treatment with intrauterine transfusion, neonates were randomly assigned for IVIg (0.75 g/kg) or placebo (5% glucose). The primary outcome was the rate of exchange transfusions. Secondary outcomes were duration of phototherapy, maximum bilirubin levels, and the need of top-up red-cell transfusions. RESULTS: Eighty infants were included in the study, 53 of whom (66%) were treated with intrauterine transfusion(s). There was no difference in the rate of exchange transfusions between the IVIg and placebo groups (7 of 41 [17%] vs 6 of 39 [15%]; P = .99) and in the number of exchange transfusions per patient (median [range]: 0 [0–2] vs 0 [0–2]; P = .90) or in duration of phototherapy (4.7 [1.8] vs 5.1 [2.1] days; P = .34), maximum bilirubin levels (14.8 [4.7] vs 14.1 [4.9] mg/dL; P = .52), and proportion of neonates who required top-up red-cell transfusions (34 of 41 [83%] vs 34 of 39 [87%]; P = .76). CONCLUSIONS: Prophylactic IVIg does not reduce the need for exchange transfusion or the rates of other adverse neonatal outcomes. Our findings do not support the use of IVIg in neonates with rhesus hemolytic disease.