We studied 160 Hepatitis C virus (HCV)-positive patients with NHL (59 indolent NHL, 101 aggressive). Median age was 67 years. HCV-RNA was present in 146. HBsAg was positive in seven patients. At diagnosis, ALT value was above UNL in 67 patients. One hundred and twenty patients received an anthracycline-based therapy, alkylators, 28 received chemotherapy plus rituximab. Cytotoxic drugs dose was reduced in 63 patients. Among 93 patients with normal ALT at presentation, 16 patients developed WHO grade II-III liver toxicity. Among 67 patients with abnormal ALT, eight patients had a 3.5 times elevation during treatment. Among 28 patients treated with rituximab and chemotherapy, five patients (18%) developed liver toxicity. Thirty four patients (21%) did not complete treatment (eight for liver toxicity). Median progression-free survival (PFS) for patients who experienced liver toxicity is significantly shorter than median PFS of patients without toxicity (respectively, 2 years and 3.7 years, P 5 0.03). After a median F-UP of 2 years, 32 patients died (three for hepatic failure). A significant proportion of patients with HCV1 NHL develop liver toxicity often leading to interruption of treatment. This could be a limit to the application of immunochemotherapy programs. HCV1 lymphomas represent a distinct clinical subset of NHL that deserves specific clinical approach to limit liver toxicity and ameliorate survival. Am. J. Hematol. 85:46-50, 2010. V