To evaluate the prevalence of hepatitis C virus (HCV) and/or hepatitis B virus (HBV) infections in HIV-infected patients in China, an epidemiological serosurvey was conducted from May 2007 to September 2008 using a random cluster sampling design of infectious disease hospitals in seven high HIV-prevalent provinces (municipalities). Univariate analysis and logistic regression were used to study the determinants of HIV and HBV and/or HCV co-infection. The overall prevalence was 41·83% (95% CI 40·36-43·30) for anti-HCV and 12·49% (95% CI 11·50-13·48) for HBsAg, respectively. The prevalence of anti-HCV and HBsAg varied according to the route of HIV transmission. Compared to those with sexually acquired HIV infection, intravenous drug users and blood donors/recipients had the greatest risk of carrying anti-HCV. Needle sharing and unprotected sexual exposures are important modes of transmission for HBV. Further interventions including health education and harm reduction strategies should be implemented in high-risk populations.