A cross-sectional study was carried out on the sera of 88 active intravenous drug users (IVDU) collected between 1985 and 1986 to evaluate the circulation of HCV genotypes in Western Sicily. The patients were grouped by age and classified by their HIV status. Genotype 3a (48.8% of all cases) was most frequently detected, followed by genotype 1a (20.4%) and type 1b (17.0%). No significant differences in HCV genotype distribution were observed between HIV positive and negative individuals. Next, the HCV genotype distribution found in sera samples of IDVUs drawn between 1985 and 1986 was studied and divided into three age groups. The genotype distribution in the younger group was then compared with samples collected ten years later, between 1995 and 1996, from young HIV negative IVDU individuals. A different distribution between HCV genotypes 3a and 1a was found with a relative, though not significant, increase in the detection of genotype 1a (38%). Finally, sera from six IVDUs obtained at three different times over a ten-year period were genotyped for HCV. None of the subjects showed any change in the genotype found at the first sampling throughout the ten years. The results suggest that a) genotype 1a and 3a are the most common among IVDUs in Western Sicily, b) concurrent HIV infection does not seem to influence HCV genotype and c) infected IVDUs harbor almost exclusively one genotype.