[APA 5/26/98: The initial starting dose of DMP 266 for patients in Cohort II is higher than the initial starting dose for patients in Cohort I.] [APA 12/21/98: The initial starting dose for patients in Stratum 1 of Cohort II is higher than the initial starting dose for patients in Cohort I and Stratum 2 of Cohort II.] The initial target AUC for DMP 266 is between 190 and 380 micromoles/h (uM/h). The initial starting dose (based on a 70 kg patient and adjusted for each patient's weight) for the first 6 patients is adjusted on the basis of tolerability and plasma concentrations of DMP 266 after 2 weeks of daily doses. If at least 4 of the first 6 patients attain a tolerable dose (dose at which no more than 2 of 6 patients experience Grade 3 or worse toxicity) and target AUC, additional patients may continue to be accrued. However, if any of the initial 6 patients experience life-threatening toxicity, further accrual is suspended. [APA 5/26/98: An assessment of the tolerability and plasma concentrations of EFV is not required in an initial group of Cohort II patients. Individual dose is based on pharmacokinetic sampling.] Patients receive a given starting dose of DMP 266 and continue on that dose until individual dose adjustments are needed. If a patient's starting dose is tolerated but the target AUC is not achieved, the dose is increased. If the starting dose is well tolerated and target AUC achieved, no adjustment in starting dose is given to future patients. If no tolerated dose achieving at least an AUC of 150 micromoles/h is reached in 4 of 6 patients, the study is suspended and alternative dosing regimens, e.g., twice-daily dosing, are considered.