The aim of the study was to assess the incidence and the cumulative probability of cytolytic and cholestatic hepatotoxicity during antiretroviral treatment in a group of HIV HCV haemophiliacs. We evaluated 47 patients that received 246 courses of antiretroviral treatment [98 courses of pre-highly active antiretroviral therapy (pre-HAART) and 148 HAART treatments]. Liver function tests were assessed at baseline of each treatment, after 1 month and at least every 4 months thereafter. Cytolytic and cholestatic hepatotoxicity was recorded. Of the 246 treatments, 28 (12.45%) were followed by cytolytic hepatotoxicity and 32 (13%) by cholestatic hepatotoxicity. Cytolytic hepatotoxicity was similar in HAART (16/148; 10.8%) and in pre-HAART treatment (12/98; 12.2%) and cholestatic hepatotoxicity was more frequent in HAART (29/148; 19.6%) than in pre-HAART treatment (3/98; 3.1%) (P < 0.001). The actuarial probability of developing cytolytic and cholestatic hepatotoxicity at 10 years of onset of antiretroviral treatments was 39% and 56%, respectively. Most enzyme elevations were asymptomatic, but in eight cases therapy was discontinued or changed and in one case a cirrhotic patient died of progressive liver failure. In HIV HCV haemophiliacs, the cumulative probability of developing hepatotoxicity during follow-up is high and although in the most cases the toxicity is mild, fatal cases can occur.