All patients in the study will take didanosine twice a day, stavudine twice a day and efavirenz once a day. All patients will also take hydroxyurea twice a day, but some will take a low dose of the drug, while others will take a high dose. Within each of these two groups (high and low dose) some patients will start taking hydroxyurea the same day they begin the anti-HIV drugs; others will not start hydroxyurea until after they have taken the anti-HIV drugs for 5 weeks. Patients will have a physical examination every 3 weeks until week 12, then every 4 weeks until week 24, and then every 8 weeks until the end of the study. Blood tests to measure virus levels will be done every other day for the first 7 days and periodically after that. For the first 8 weeks after starting hydroxyurea, blood tests will be done weekly. An eye examination, chest X-ray, electrocardiogram, and CT scans of the head will be done about every 6 months.