One of frequently occurring hematological disorders accompanying advanced liver diseases is thrombocytopenia (TP). Immunological disorders in patients with liver cirrhosis, loss of tolerance to own antigens, and the change of platelet antigenicity enable antiplatelet antibody formation under the influence of continuous activation. The aim of the study was to determine the rate of autoimmunological thrombocytopenia occurrence in patients with liver cirrhosis and TP. Antiplatelet autoantibody occurrence were determined in blood serum with the use of ELISA method in 15 patients with liver cirrhosis and TP (mean plt number 67.9 +/- 24.9 x 10(3)/microliter). Three patients (20%) presented anti-GPIIb/IIIa antibodies and 2 patients--anti-GPIa/IIa. These patients had liver failure (stage C according to Child-Pugh classification) and splenomegaly. Plt morphological parameters were also evaluated. The significant decrease of plt crit as well as the decrease of mean platelet volume (MPV) was observed in liver cirrhosis with thrombocytopenia. The increase of megathrombocyte population (MPV > 20fl) up to 5.5% of all plt was also observed. Megathrombocytes in healthy individuals were 2.25% of platelet population. Examinations confirmed that autoimmunological factors play an important role in the development of thrombocytopenia in liver cirrhosis.