Human immunodeficiency virus (HIV)-infected patients are routinely being treated with combinations of 3 or 4 drugs (highly active antiretroviral therapy [HAART]), to reduce the risk of viral resistance development. Development of new potent antiretroviral (ARV) drugs is urgently needed to prolong suppression of viral replication in subjects infected with HIV. This is a Phase I, open-label, parallel, controlled, sequential study to investigate the single-dose and steady-state pharmacokinetics, and short-term safety and tolerability of TMC278 in subjects with mild or moderate hepatic impairment compared to subjects with normal hepatic function. The trial aims to provide guidance on administration and dose recommendations of TMC278 in subjects with mildly or moderately impaired hepatic function. The study population will consist of a total of 32 male and female subjects between 18 and 65 years. Panel A will consist of 8 subjects with mild hepatic impairment and 8 healthy subjects matched for sex, age (± 5 yrs), and BMI (± 15%). Panel B will consist of 8 subjects with moderate hepatic impairment and 8 healthy subjects matched for sex, age (± 5 yrs), and BMI (± 15%). Treatment in Panel A and Panel B will be conducted sequentially. Subjects in Panel A will receive a TMC278 25 mg tablet once daily for a total of 11 days. Recruitment for subjects for Panel B will start after evaluation of the safety, tolerability and pharmacokinetic data from subjects in Panel A. The anticipated dose of TMC278 to be administered to subjects in Panel B is the same dose as for Panel A (25 mg once daily for 11 days), but this dose might be adjusted depending on the results of Panel A.