Because hepatitis C virus (HCV) and human immunodeficiency virus (HIV) share common transmission pathways, HIV-HCV co-infection is frequent, involving about 40% of seropositive subjects particularly injection drug users and patients with hemophilia. We performed a retrospective analysis on clinical, epidemiological and therapeutical aspects in a population of HIV-HCV coinfected patients, observed in our Department during the period 2001-2003. Forty per cent of 404 observed patients had a co-infection; 90% of those were drug addicts and most (90.2%) were on HAART treatment. Seventy-three per cent of co-infected patients showed transaminases alterations, and 85% had detectable viremia. Prevalent genotypes were 1 (44.6%) and 3 (36.4%). The association PEG-IFN and ribavirine obtained sustained responses in 55% of 9 treated patients.