BACKGROUND: Laminin-1, a multifunctional glycoprotein of the basement membrane, is thought to be important in embryogenesis, embryonic implantation, and placentation. We recently showed that serum IgG anti-laminin-1 autoantibodies (auto-Abs) are associated with recurrent first-trimester miscarriages. The present study assessed the clinical significance of anti-laminin-1 Abs with infertility, accompanied with or without endometriosis. METHODS: Sixty-eight infertile patients who underwent laparoscopy or laparotomy and 39 healthy non-pregnant women were tested for IgG anti-laminin-1 Abs. The association between the Abs and endometriosis was analysed. The presence of laminin-1 mRNA was detected in endometriotic lesions. RESULTS: Twenty infertile patients were positive for anti-laminin-1 Abs. The Ab levels in those patients were significantly higher than those in healthy non-pregnant women (P = 0.0005). The presence of the Abs was significantly associated with endometriosis in those patients (P = 0.0096). The Abs recognized a particular domain, i.e., the laminin-alpha1 chain G domain. mRNA encoding laminin-alpha1, -beta1, and -gamma1 chains was expressed in 90% of endometriotic lesions. CONCLUSIONS: IgG anti-laminin-1 Abs were significantly associated with endometriosis in infertile patients. The Abs might be clinically important in the development of autoimmune-mediated reproductive failures and the assessment of the Abs may provide a novel non-invasive diagnosis of endometriosis.