The presence of the lupus anticoagulant was diagnosed in six pregnant women because they had prolonged activated partial thromboplastin and kaolin clotting times which could not be corrected by dilution of test samples with normal plasma. All previous pregnancies (14) had ended in intrauterine death in the five multigravidas. Three women had had thrombotic episodes during pregnancy. The diagnosis of SLE was established in four. Antinuclear antibody was identifiable in all 6. All were treated with prednisone 40-60 mg/day and aspirin 75 mg/day. Suppression of the lupus anticoagulant activity was achieved in five patients, all of whom gave birth to live infants. In the sixth patient suppression of the anticoagulant activity was demonstrated between pregnancies; a further pregnancy in this patient was lost before she had received sufficient prednisone to suppress the anticoagulant. Since treatment with prednisone and aspirin can lead to successful pregnancies, it is important to screen all women with SLE, thrombotic episodes, recurrent intrauterine deaths, or a biologically false-positive VDRL for the presence of the lupus anticoagulant.