Both chronic hepatitis C and nevirapine (NVP) use are risk factors for transaminase elevation under highly active antiretroviral therapy. NVP is metabolized in the liver and its clearance could be altered in the presence of chronic hepatitis C virus (HCV) infection, enhancing the risk of liver toxicity. We examined NVP plasma levels in 70 HIV-infected subjects receiving NVP-containing triple combinations. The median (range) NVP plasma trough concentrations were similar in 32 HCV antibody-positive and 38 HCV antibody-negative patients (5.8 [0.7-29] vs. 6.1 [0.9-9.6] microg/ml). Thus, HCV coinfection itself does not seem to influence significantly the pharmacokinetics of NVP in HIV-infected subjects.