Data are presented to define a unique group of preeclamptic/eclamptic patients with the finding of hemolysis (H), elevated liver enzymes (EL), and a low platelet count (LP). This entity has been termed the HELLP syndrome and may occur when the usual clinical findings to diagnose severe preeclampsia are absent. Often the patient is given a nonobstetric diagnosis and treatment is withheld or modified. The possible pathophysiology of this syndrome, the management of the patient, and the maternal and neonatal outcomes are presented. Recognition of the clinical and laboratory findings of the HELLP syndrome is important if early, aggressive therapy is to be initiated to prevent maternal and neonatal death. The practicing obstetrician must be knowledgeable about this severe consequence of hypertension in pregnancy.