To evaluate the presence in serum and the clinical relevance of several antinuclear autoantibodies, we investigated 31 patients with initially diagnosed gastric cancer and 40 age-matched healthy controls. Autoantibodies against ssDNA, dsDNA, cardiolipin, actin, myosin, tropomyosin, GM1, GD1b and GT3 gangliosides, were detected with an enzyme-linked immunoassay (ELISA). Anti-ssDNA, anti-actin, anti-GM1 and anti-GD1b antibodies were detected in the serum of 11 (p = 0.001), 8 (p = 0.02), 11 (p = 0.001), and 9 (p = 0.008) patients with gastric cancer, respectively. There was no significant difference between patients with cancer and the control group, as far as the other autoantibodies were concerned. Most of the patients (90%) had autoantibodies against at least one of the antigens examined. Patients with anti-ssDNA, anti-actin, anti-GM1 and anti-GD1b antibodies were less likely to survive than the patients being negative to the above autoantibodies: the figures are 1 of 11 (9%) compared with 4 of 20 (20%); 1 of 8 (13%) compared with 5 of 23 (22%); 1 of 11 (9%) compared with 4 of 20 (20%); and 1 of 9 (11%) compared with 4 of 22 (18%), respectively. Our findings suggest that 4 of the 9 autoantibodies that we assayed are significantly more likely to be found in serum of patients with gastric cancer, indicating that the immune system has a role in the process of the malignant disease. If our results are confirmed by forthcoming studies, some of the immunological variables that we examined could be used as markers of prognostic value in patients with gastric cancer.