The average time until the resolution of thrombocytopenia, which as a part of HELLP syndrome accompanies 4-16% of cases of severe preeclampsia, has not been defined previously. We followed 25 patients with severe preeclampsia, platelet counts below 100,000/microL, and elevated liver enzymes until their platelet counts returned to levels above 100,000/microL. Among severe preeclamptics who did not receive platelet transfusions, the average time from delivery to the resolution of thrombocytopenia was 60 hours, and all had platelet counts above 100,000/microL by 95 hours. Seven patients were followed after their platelet counts exceeded 340,000/microL; all showed a rebound phenomenon, with platelet counts reaching values of 413,000-871,000/microL.