Immunopathologic reactions may occur during toxocariasis due to tissue invasion and destruction by the secretions of larvae containing various enzymes with broad spectrum. The aim of this study was to search for autoantibodies such as anti-nuclear (ANA), anti-mitochondrial (AMA), anti-smooth muscle (ASMA), anti-neutrophil cytoplasmic (ANCA), anti-myeloperoxidase (MPO) and liver-kidney microsomal type 1 (LKM-1) antibodies in patients with toxocariasis, in order to investigate the role of toxocariasis as a trigger factor for autoimmune reactions. Forty patients (22 were male; mean age: 35.6 +/- 10.7 years) diagnosed as toxocariasis by clinical findings (abdominal pain, allergic symptoms and/or eosinophilia, without detection of any other causative agents, and without liver dysfunction, diabetes mellitus, cardiac or renal failure, and autoimmune disease) and in-house ELISA positivity and 32 healthy controls (16 were male; mean age: 40.7 +/- 11.2 years) were included to the study. ANA (screen), dsDNA, SS-A. SS-B, Scl-70, LKM-1, MPO and M2 autoantibodies have been investigated by ELISA (Euroimmun, Germany), while ANCA, AMA and ASMA antibodies by indirect immunofluorescence (IMMCO, NY) methods. Autoantibody positivity was detected in 18 (45%) patients of whom I I yielded a single type, and 7 yielded >= 2 types of autoantibodies. This rate was 12.5% for control group (two subjects were positive for ANA-Screen, one for anti-M2 and one for anti-LKM-1). The difference between the total positivity rates in patient and control groups was found statistically significant (chi(2) = 5.72, p = 0.004). The most frequent autoantibody type among patients were ASMA (n = 6), followed by anti-dsDNA (n = 5). anti-M2 (n = 5), anti-SS-B (n = 4), anti-LKM-1 (n = 3), anti-SS-A (n = 2), ANCA (n = 2) and anti-MPO (n = 1). Positivity rate for ASMA was found statistically significant in patients' group compared to controls (chi(2) = 12.24, p = 0.03), while there was no significant difference between the groups in terms of other autoantibody rates (p > 0.05). These data could be related to the possible release of autoantigens following muscle tissue injury during toxocariasis and/or antigenic mimicry of parasitic products during the infection in which muscle invasion is frequently seen. In conclusion, since autoantibodies are frequently detected in toxocariasis, this situation should be taken into consideration in the presence of autoantibodies.