All patients receiving NVP will start at 200 mg once daily for 2 weeks, because it has been demonstrated that this lead-in dosing regimen reduces the frequency of NVP-induced rash. At Visit 3 (Week 2), patients increase the NVP dose to either 200 mg twice daily or to 400 mg once daily. Patients receiving ATZ/r will be treated with ATZ 300 mg once daily, boosted by 100 mg ritonavir (RTV) once daily. Background antiretroviral therapy for all patients consists of one tablet of Truvada. Treatment duration is 48 weeks (primary endpoint) with an extension to 144 weeks. Patients may also participate in the metabolic sub-study, comparing NVP and ATZ/r for signs and symptoms of lipodystrophy and serum lipid/glycaemic abnormalities.