Didanosine is an effective anti-HIV drug, but it can cause stomach upset. This study tests a new form of didanosine, ddI EC, a coated pill that passes through the stomach more easily and hopefully will prevent stomach upset. The purpose of this study is to compare the effectiveness of ddI EC versus the standard form of ddI. Both forms of ddI will be given with stavudine (d4T) plus nelfinavir (NLF).

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.

Inclusion Criteria

You may be eligible for this study if you:

• Are HIV-positive.
• Are at least 18 years old.
• Have a viral load of at least 5,000 copies/ml and a CD4 count of at least 100 cells/mm3.

Exclusion Criteria

You will not be eligible for this study if you:

• Have received more than 4 weeks of treatment with nucleoside anti-HIV medications (NRTIs), or more than 1 week with protease inhibitors. (All anti-HIV treatments other than study medications must be stopped at least 14 days prior to study entry.)
• Have severe diarrhea.
• Are pregnant or breast-feeding.
• Have a history of pancreatic disease or any other serious condition.
• Have hepatitis within 30 days prior to study entry.
• Cannot take medications by mouth.
• Have received certain medications.