TMC435 is being investigated for treatment of chronic HCV infection, in combination with Peg-IFN (pegylated interferon) and RBV (ribavirin). About 30% of all HIV infected patients are co-infected with HCV and need treatment for both infections. The results of this study will provide dosing recommendations for coadministration of TMC435 and TMC278 or Tenofovir in HCV-HCV co-infected patients. This is a Phase I, open-label (both participant and investigator know the name of the medication given at certain moment), randomized (sequence of treatment with study medications is assigned by chance), crossover trial in 48 healthy participants to investigate the pharmacokinetic interaction between TMC435 and an antiretroviral agent (TMC278 or tenofovir), at steady state. The participants are being allocated to one of two panels. In Panel 1, participants will receive three treatments (treatment A-B-C) in a randomized order. Participants will receive TMC435 150 mg q.d., TMC278 25 mg q.d.and TMC278 25 mg q.d. + TMC435 150 mg q.d., respectively. All treatments will be administered for 11 days and with food. There will be a washout period (a period where no study drug will be taken in view of having all the medication eliminated from the body before starting a new treatment) of at least 14 days between last intake of study medication in one session and first intake of study medication in the subsequent session. In Panel 2, participants will receive three treatments (treatment D-E-F) in a randomized order. Participants will receive TMC435 150 mg q.d., TDF 300 mg q.d. and TDF 300 mg q.d. + TMC435 150 mg q.d., respectively. All treatments will be administered for 7 days and with food. There will be a washout period of at least 7 days. Pharmacokinetic profiles of all three compounds will be determined through blood samples taken at regular intervals during the study. Safety and tolerability will be assessed during the study period and in follow-up. Blood and urine samples, electrocardiogram (ECG) and vital signs (blood pressure and heart rate) will be taken at screening, before medication intake on days 1 and 11 and on Day 12 in each session of Panel 1, before medication intake on days 1 and 7 and on Day 8 in each session of Panel 2, 5 hours post dose on Day11 and Day 7 in Panel 1 and 2, respectively and at the 2 follow up visits at 1 week and 4-5 weeks after last dose of study medication in the last session. A physical examination will be performed at screening, on day -1 (= day before first medication intake in each session for both panels) and during the 2 follow up visits. Each volunteer will receive 3 treatments for 11 or 7 days (Panel 1 and 2, respectively), minimum 14 or 7 days apart from each other (Panel 1 and 2, respectively). Volunteers in Panel 1 will take oral TMC435 150 mg q.d., oral TMC278 25 mg q.d. and combined. Volunteers in Panel 2 will take oral TMC435 150 mg q.d., oral TDF 300 mg q.d. and combined.