Summary. Twenty-five per cent of individuals infected with hepatitis C virus (HCV) are able to clear HCV spontaneously. Differences in host genetics are believed to affect the outcome of HCV infection. We analysed an exonic, a promoter and an intronic single nucleotide polymorphism (SNP) of the interferon-¿3 coding interleukin (IL)-28B gene to study the relationship between IL28B SNPs and outcome of HCV infection. Among 206 HIV-1-infected Europeans with evidence of HCV infection, 47 (23%) individuals had cleared HCV and 159 (77%) had developed chronic infection. The exonic rs8103142 CT, the promoter rs12979860 CT and the intronic rs11881222 AG genotypes were associated with a decreased HCV clearance rate with adjusted odds ratios (aOR) of 0.3 (95% CI, 0.1-0.7), 0.4 (95% CI, 0.2-0.8) and 0.4 (95% CI, 0.2-0.8), respectively. The haplotype block TCG CTA was associated with a decreased HCV clearance rate (aOR 0.4, 95% CI, 0.2-0.8). Further, we found significant differences in HCV RNA levels among individuals chronically infected with HCV genotype 1 for rs8103142 and rs12979860 (P = 0.05). Chronically infected individuals with HCV genotype 3 and with the favourable haplotype block CTA CTA had higher median HCV RNA levels than individuals with unfavourable haplotype blocks (P = 0.05). Our findings suggest that IL28B may account for some differences in HCV outcome but that other factors including the viral genotype, host genetics and the host-virus interaction are likely to influence the outcome of HCV infection.