Introduction The aims of this study were to estimate the prevalence of HIV and hepatitis virus coinfection in the Spanish population and to determine the percentage of patients who are candidates for chronic hepatitis C virus (HCV) treatment and liver transplantation within this population. Methods A cross-sectional study was performed in 2002 in two Spanish populations of HIV-infected patients: 1,260 patients from 39 centers throughout Spain (P1) and 1,560 patients from three tertiary teaching hospitals in Madrid (P2). Results The following hepatitis A virus (HAV), hepatitis B virus (HBV) and HCV serological prevalence were found in the P1 and P2 groups, respectively: HAV-IgG antibodies: 74% and 78%; HBsAg+: 4.9% and 4.8%; HBsAg−, anti-HBc+, anti-HBs+: 39% and 39%; HBsAg−, anti-HBc+, anti-HBs−: 25% and 31%; HBsAg−, anti-HBc−, anti-HBs+: 7% and 8%; HBsAg−, anti-HBc−, anti-HBs−: 22% and 16%. Anti-HCV+: 61% and 65%, respectively. Of the patients with positive HCV serology, 88.8% and 84.6% of each group were positive for HCV-RNA by polymerase chain reaction. Multiple coinfections with hepatitis viruses were found in 3.2% and 2.8%, respectively; of these, 70% and 78% had coinfection with HBV, HCV and HDV. Liver cirrhosis was found in 5.8% and 9.6% of the patients coinfected with HIV and HCV, respectively. Liver transplant was indicated in approximately one out of every six coinfected patients with liver cirrhosis. The 43 and 37% of the HCV coinfected patients were good candidates for anti-HCV treatment, but only 14% and 15% of patients had initiated it. Conclusions A high percentage of HIV-infected patients in Spain were coinfected with hepatitis viruses, especially HCV. The number of possible candidates for liver transplantation is rising and could increase in the next few years. In the future, greater efforts to treat HIV-and hepatitis virus-coinfected patients will be required.