[APA 12/21/98: The dose of NFV is the same for patients in Cohort I and Stratum 2 of Cohort II; the dose for patients in Stratum 1 of Cohort II is higher.] The minimum target AUC for NFV is 10 mg x h/L. Doses are adjusted for an individual child if AUC falls below threshold at Week 2 or 6. Children with weight no greater than 30 kg receive a lower dose than children with weight greater than 30 kg or Tanner Stage IV. [APA 5/8/00: The first group of 6 patients receives the initial dose of NFV. If none of the 6 patients falls below the target AUC, the remainder of the sample is accrued and treated at this dose. If more than 1 of the 6 patients fall below the target AUC, then another group of 6 patients is accrued and treated at the next higher dose. If exactly 1 of the 6 patients falls below the target AUC, 2 more patients are accrued and treated at the same dose. If 1 of these 2 patients falls below the target AUC, another group of 6 patients is tested on the next higher dose. If neither of these 2 patients falls below the target AUC, then the remainder of the sample is accrued and treated at this dose. The dose is escalated until a dose that meets the above criteria is achieved or further dose escalation is prohibited due to toxicity.] The duration of therapy is 48 [APA 12/21/98:104] [APA 5/8/00: 208] weeks.