Serum samples from 70 patients with two or more early spontaneous abortions and, for comparison, sera from 20 healthy and fertile women were assayed by indirect immunofluorescence for the presence of antibodies to sperms and genital organ antigens and for non-organ specific and organ specific antibodies. All sera were tested for thyreoglobulin antibodies by hemagglutination. The frequency of sperm antibodies and autoantibodies was significantly higher in patients with recurrent abortions than in the control group. There was no relation between the type or titer of antibodies and the clinical data of the patients.