Autoimmune diseases are suspected of causing some cases of recurrent pregnancy loss. We sought serological evidence of such diseases in women with recurrent pregnancy wastage. Antinuclear antibodies were studied administrating indirect immunofluorescence test using HEP-2 cells as targets. We compared the frequency of a low-level antinuclear antibody titers in the 68 women with a history of unexplained recurrent pregnancy losses (group A) to that in 35 with explained repeated pregnancy losses (group B) and 44 healthy pregnant (group C), and 36 healthy nonpregnant women (group D). The frequency of positive ANA tests at a titer of 1:40 or higher was 51.5% in group A, 34.3% in group B, 6.8% in group C and 5.6% in group D. No negative influence on pregnancy outcome was found in case of occurrence of ANA in group A where women were treated with husband's lymphocyte immunisation. The success rate was 78.6% in patients with positive ANA and 62.5% in patients with negative ANA. This study demonstrates a high prevalence of low-titer antinuclear antibody-positive serum in patients with both explained and unexplained pregnancy losses; however, the significance of these findings remains unclear.