Hepatitis C virus-infected haemophiliacs are traditionally under represented in international treatment studies thus data assessing response to pegylated-interferon (peg-IFN) and ribavirin (RBV) in HCV mono-infected or HCV/HIV co-infected haemophiliacs are few. Since 2001, 37 haemophiliac patients have received peg-IFN and RBV according to centre-based investigator initiated protocols. Primary end points were: early virological response (EVR); end of treatment response (EOTR) and sustained virological response (SVR). An intention-to-treat analysis was used. Secondary end points were adverse events, haemopoietic stem cell growth factor use, therapy discontinuations and dose reductions. Hepatitis C virus mono-infection group (Mono-I) numbered 20 (60% genotype 1). HCV/HIV co-infected group (Co-I) numbered 17 (59% genotype 1/4). Primary end points were: EVR 76%, EOTR 70% and SVR 43%. Comparison of Mono-I to Co-I demonstrated: EVR rates of 70% and 82%, respectively; EOTR rates of 65% and 76%, respectively, and SVR rates of 35% and 53%, respectively. SVR rates genotype 1/4 group - 17% (Mono-I) vs. 30% (Co-I); SVR rates genotype 2/3 group - 63% (Mono-I) vs. 86% (Co-I). Therapy discontinuations: six of 20 (30%) Mono-I vs. three of 17 (18%) Co-I. Dose reductions: two of 20 (10%) Mono-I vs. zero of 17 Co-I. Haematological support factor use: one of 20 (5%) Mono-I vs. four of 17 (23.5%) Co-I. Virological outcomes to peg-IFN and RBV in HCV-infected haemophiliacs are comparable to published data relating to other HCV-infected cohorts. Good virological outcomes can be achieved in HIV co-infected haemophiliacs particularly when growth factors are used to facilitate full dosing of peg-IFN and RBV.