Organ- and disease-specific cardiac autoantibodies are found in a third of dilated cardiomyopathy patients from the U.K. and Italy and represent markers of autoimmune involvement. The role of autoimmunity may vary in dilated cardiomyopathy patients from different countries due to differences in genetic susceptibility to autoimmune diseases. The aim of this study was to assess the frequency of organ-specific cardiac autoantibodies detected by immunofluorescence in a consecutive series of patients with dilated cardiomyopathy and in disease and normal control subjects from Poland. The study groups included 79 patients with idiopathic (WHO criteria) dilated cardiomyopathy, 55 patients with other cardiac disease and 60 normal subjects. Cardiac antibody tests were performed by indirect immunofluorescence on human heart; skeletal muscle was used to identify cross-reacting antibodies. The frequency of organ-specific cardiac autoantibodies was higher in patients with dilated cardiomyopathy (21/79, 27%) than in controls with other cardiac disease (1/55, 2% P < 0.001) or in normal subjects (7/60, 12% P < 0.02). Conversely, cross-reactive antibodies were detected in similar proportions in patients with dilated cardiomyopathy (5/79, 6%), disease controls (7/55, 13%) and normal subjects (6/60, 10%, P = ns). The organ-specific antibody was more common in patients with dilated cardiomyopathy with insidious onset of disease (17/34, 50%) compared to those who did not exhibit this feature (4/45, 9%, P < 0.0001). Organ- and disease-specific cardiac autoantibodies were found in 27% of Polish patients with dilated cardiomyopathy at diagnosis; this is evidence for autoimmune involvement in a subset of patients from our country, as seen in a previously reported series of Western European origin. The association of antibody status with insidious onset of symptoms is in keeping with the long latency period observed in other autoimmune disorders.