In view of the association between pre-eclampsia and disseminated intravascular coagulation, three patients presenting with severe pre-eclampsia before the 28th week of pregnancy were treated with heparin. In all three patients, there was deterioration of hypertension and proteinuria that necessitated the withdrawal of treatment after five to six days. During treatment, serum and urinary fibrinolytic degradation products (FDPs) continued to rise or remained unaltered, plasminogen levels showed a steady fall, and the platelet count remained at a reduced level. These data suggest that heparin was an ineffective form of treatment and did not prevent the intravascular fibrin deposition associated with severe pre-eclampsia.