We reviewed the sonograms and medical records of all patients who underwent intrauterine transfusions between December 1981 and December 1984 in order to determine the time course for disappearance of the intraperitoneal blood. Seventy-two sonographic examinations were performed on 22 patients who underwent 51 intrauterine transfusions. Nonhydropic fetuses who received less than or equal to 50 cc of intraperitoneal blood exhibited no ultrasonic evidence of intraperitoneal fluid after 8 days. Nonhydropic fetuses receiving greater than 50 cc of intraperitoneal blood showed resolution of intraperitoneal fluid after 12 days. Hydropic fetuses, after intraperitoneal transfusion, all demonstrated persistence of intraperitoneal fluid. Intraperitoneal fluid was seen as long as 24 days after transfusion in hydropic fetuses.