Patients are randomized to 1 of 2 open-label treatment groups. Group 1 receives ddI EC plus d4T plus NLF for 48 weeks. Group 2 receives ddI plus d4T plus NLF for 48 weeks. Both forms of ddI are administered orally once daily. Antiviral activity is determined by the magnitude and the duration of reduction of plasma HIV RNA from baseline through Week 24.