Four hundred and fifty-four gravid women were identified with the HELLP syndrome from January, 1980 to May, 1992. The peak systolic and diastolic blood pressures, proteinuria, and uric acid were recorded for each patient during the peripartal course. Patients were classified according to disease severity with, in addition to elevated lactate dehydrogenase (LDH) values, laboratory evidence of haemolysis and hepatic dysfunction, a peripartal platelet count < or = 50,000/microliters was depicted Class I, Class II as a platelet count > 50,000 and < or = 100,000/microliters and Class III as > 100,000 and < or = 150,000/microliters. Patients with Class I HELLP syndrome had peak antepartum systolic blood pressures < 150 mm Hg significantly more often than the Class II (p < 0.0091) or Class III (p < 0.04) HELLP syndrome. Class I HELLP syndrome had significantly more patients with 1+ to 2+ proteinuria than Class II (p < 0.02) and Class III HELLP syndrome (p < 0.009). Uric acid levels were not different among nor proportionately related to increasing severity of the HELLP syndrome.