Cohorts of six patients each receive escalating doses of sCD4-PE40 in a single IV weekly dose for 8 weeks. All six patients at a given dose must complete 2 weeks of therapy without dose-limiting toxicity before dose escalation in subsequent patient cohorts may occur. The MTD is defined as the dose of sCD4-PE40 immediately below that at which two or more of six patients experience grade 3 or higher toxicity or one or more of six patients experience grade 4 toxicity. After the MTD for the once-weekly schedule is reached, subsequent cohorts receive escalated doses of sCD4-PE40 on a 5x weekly schedule for approximately 4 weeks, in an attempt to establish the MTD for that schedule. When an MTD has been determined for the 5x weekly schedule, and if antiretroviral activity is observed, six additional patients receive this dose combined with AZT for 4 weeks.