We have studied, prospectively, the incidence of several antiphospholipid antibodies (lupus anticoagulant, anticardiolipin, anti-phosphatidylserine, anti-phosphatidic acid, anti-phosphatidylinositol and anti-thromboplastin antibodies) in 65 consecutive patients with two or more (range 2-8, mean 3.1) abortions. Lupus anticoagulant activity was detected in seven (10.7%) patients and all of them exhibited other antiphospholipid antibodies. Of the previous pregnancies in these seven women, 88% had ended in spontaneous abortion. Four of them achieved pregnancy after low-dose aspirin therapy was started, and carried successfully to term. It is concluded that antiphospholipid antibodies, namely lupus anticoagulant, should be routinely screened in the recurrent spontaneous aborter.