 Comparison: HIV-infected children less than 24 months of age, exposed to any pMTCT regimen that included NVP and who achieve and maintain viral suppression for at least 3 months with a PI-based regimen will be randomized to one of the two groups: 1 to continue on PI-containing regimen or 2 to be switched off the PI-containing regimen onto the NVP-containing regimen. The study outcome will be proportions in the two groups who have complete virologic suppression at 6 months after randomization. 