The accumulation of individual hepatitis C virus (HCV) proteins in the liver cells of patients with acute hepatitis C (AHC) and their association with the course and outcome of the disease were studied. AHC protein expression in the cryostat liver sections from 20 patients with AHC was estimated by immunohistochemical assay using original monoclonal antibodies to 5 HCV proteins (core, NS3, NS4A, NS4B, and NS5A). The results of HCV detection in the patients were compared with their biochemical, clinical, and morphological findings. HCV proteins were totally revealed in the livers of all the patients, individual proteins were identified with a frequency of 89-95%, which is significantly more than those in patients with chronic hepatitis C. The hepatic expression of core protein was shown to inversely correlate with the duration of an acute period. There was a direct relationship between the accumulation of core, NS3, and NS5A proteins and the liver tissue damage caused by stepwise necrosis rather than intralobular necrosis. The presumed convalescence was ascertained to be associated with the larger count of hepatocytes containing the proteins NS4A and NS3 early after AHC manifestation.