5. hydroxyurea (higher dose) plus ddI. After the completion of week 12, patients on combination therapy remain on their current therapy and patients on ddI plus placebo have hydroxyurea replace the placebo at 1 of 2 assigned doses (1:1 randomization). AS PER AMENDMENT 5/5/97: If after the 24-week treatment period, a patient has an RNA level less than or equal to 5,000 copies/ml or less than 20,000 copies/ml with a greater than 1 log10 decline from baseline, she has the option to continue therapy open-label ddI plus hydroxyurea for an additional 24 weeks.