Healthy volunteers will receive the OC once daily for 21 days for at least 1 OC cycle prior to Day 1 [stabilizing OC cycle from Day -28 to Day -1]. During the second OC cycle [from Day 1 to Day 28], subjects will receive the OC alone once daily for 21 days [Treatment A]. During the third OC cycle [from Day 29 to 56], subjects will receive the OC once daily for 21 days and in addition TMC278 25 mg q.d. in the morning for 15 days, starting on the first day of OC intake (Day 29) [Treatment B]. Full 24-hour pharmacokinetic profiles of ethinylestradiol and norethindrone will be determined after the first 2 weeks of the second OC cycle (Treatment A: OC alone; Day 15) and after the first 2 weeks of the third OC cycle (Treatment B: OC+TMC278; Day 43). A full 24-hour pharmacokinetic profile of TMC278 will be determined on Day 43. Blood samples on these days will be drawn just before drug intake (predose), and at 0.5, 1, 1.5, 2, 3, 4, 5 (Day 43 only), 6, 9, 12, 16 (Day 43 only) and 24 hours postdose. Safety evaluations include evaluation of adverse events, physical examination including vital signs, ECGs and laboratory hematology and biochemistry assessments. Healthy volunteers will receive a tablet of ethinylestradiol and norethindrone OC once daily for 21 days for at least 1 OC cycle prior to Day 1. During the second OC cycle, healthy volunteers will receive a tablet of ethinylestradiol and norethindrone OC alone once daily for 21 days. During the third OC cycle, healthy volunteers will receive a tablet of ethinylestradiol and norethindrone once daily for 21 days and in addition a tablet of TMC278 25 mg once daily in the morning for 15 days.