This is an open label study, which means that all parties including the study doctor, the healthy volunteer and the sponsor will know at all times which treatment group the volunteer is in. This is a cross over trial, which means that every volunteer will be sequentially subjected to 2 different treatments. A total of 32 healthy volunteers will participate in this study. Volunteers will be divided over 2 panels of 16 volunteers each. Volunteers in Panel 1 will be randomly assigned to treatment sequence AB or BA. Volunteers in Panel 2 will be randomly assigned to treatment sequence CD or DC. During all treatment periods 100 mg ritonavir (rtv) will be dosed once daily on Day 1 to Day 5. In treatment A you will receive a single dose of darunavir (DRV) two 400 mg commercial formulation in the morning of day 3 after a standard breakfast. In treatment B you will receive a single dose of darunavir (DRV) 800 mg new formulation in the morning of Day 3 also under fed conditions. In treatment C you will receive a single dose of darunavir (DRV) two 400 mg commercial formulation in the morning of day 3 under fasted conditions. In treatment D you will receive a single dose of darunavir (DRV) 800 mg new formulation in the morning of day 3 also under fasted conditions. Treatment sessions are organized with 7 days between treatment periods. In each session, an extensive investigation of the levels of DRV and rtv in the blood circulation is planned. Levels of DRV will be assessed at 15 different time points, i.e. before administration of DRV 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 9, 12, 24, 48 and 72 hours after intake of DRV. Levels of rtv will be assessed at 13 different time points, i.e. before administration of rtv on Day 3, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 9 and 12 hours after intake of rtv on day 3 and before administration of rtv on Day 4. Standard Safety assessments (blood biochemistry and hematology, urine analysis, ECG, pulse rate and blood pressure) will be performed on Day1, 3 and 6 in each Treatment period. Two 400 mg DRV commercial tablet formulation (F030) single dose on Day 3 of treatment A and C; 800 mg DRV new tablet formulation (G002) single dose on Day 3 of treatment B and D; 100 mg rtv capsule once daily on Day 1 to Day 5. All intake are oral.