The efficacy of examining antinuclear antibody (ANA) was investigated as a screening test detecting subclinical immune disorders in infertility and sterility. ANA was measured in 116 unexplained infertile or sterile patients. The ANA positive rate was 43.5% in group A (habitual abortion, n = 23), 38.1% in group B (consecutive miscarriages, n = 21), 30.0% in group C (one miscarriage, n = 10), 16.7% in group D (one or more deliveries n = 12) 22.0% in group E (primary sterility, n = 50), and 22.4% in the control group (n = 54). The positive rate for all the infertile patients (group A+B) was 40.9% and significantly higher than that in for the control group (p < 0.05). Ten patients with positive ANA had 12 deliveries and 20 patients with negative ANA had 23 deliveries. The frequency of preeclampsia in the patients with positive ANA was higher than in those with negative ANA (41.7% versus 4.3%, p < 0.05). A higher incidence of premature deliveries was recognized in the patients with positive ANA than in those with negative ANA (41.7% versus 8.7%, p < 0.1). Average birth weight (> 35 week) for patients with and without positive ANA was 2,976g (n = 8) and 3,122g (n = 19) respectively. The former tends to be smaller than the latter (p < 0.1).