We conducted a retrospective study to analyze the CD4 recovery of naive vertically human immunodeficiency virus-infected children with severe immunodeficiency who were followed up during at least 4 years of receiving highly active antiretroviral therapy (HAART). Children with baseline CD4 of <15% did not reach a mean CD4 of > or =25% after the 4th year on HAART. We conclude that starting HAART after severe immunosuppression of naive HIV-infected children may not be effective for recovery of normal %CD4.