 The wide use of NVP in pMTCT-prophylaxis may result in resistance to NNRTI and concomitantly limits the use of these drugs for the treatment of HIV-infected children. To avoid restricting treatment options for children, it is desirable to preserve NVP for both pMTCT and first line treatment. This study will therefore test whether resistance-caused treatment failures of HIV-infected and previously NVP-exposed children can be avoided if the NVP treatment is preceded by an initial PI-based regimen. 