In chronic hepatitis C (CHC) intercellular and vascular cell adhesion molecules-1 (ICAM-1 and VCAM-1) are expressed de novo on hepatocytes infected by hepatitis C virus and on endothelial cells from sinusoidal vessels, respectively. The soluble forms of these (sICAM-1 and sVCAM-1) reflect their level of expression in tissue. Serum levels of sICAM-1 and VCAM-1 were measured using ELISA assays in 20 patients with CHC, at baseline and after 6 months of treatment with interferon-a + ribavirin. Significantly higher mean values of both adhesions, comparing to healthy controls, were observed. In all patients the lowest value of sICAM-1 was above highest level of controls. At the beginning of the study the responders and nonresponders to treatment (at 1 year) did not differ from each others concerning sICAM-1/sVCAM-1 concentrations. A significant reduction of sICAM-1 levels was apparent after 6 months of therapy, especially in the group of responders. Just a normalization of sICAM-1 values in all but one of responders, comparing to only 5 of 9 nonresponders has been achieved. By contrast, the mean level of sVCAM-1 did not change significantly with therapy. In conclusion, the normalization of serum sICAM-1 at 6 months of treatment may be useful prognostic parameter of response to the end of the administration period (1 year).