To determine the safety and tolerability of hydroxyurea at two doses alone and in combination with didanosine (ddI). To compare the short term antiviral effect of ddI monotherapy versus hydroxyurea plus ddI, as measured by plasma RNA levels at 8 weeks of therapy. [AS PER AMENDMENT 10/1/97: Accrual to arms involving hydroxyurea alone has been closed.] Current antiviral therapies for HIV-1 are limited by a few choices, and the lack of sustained clinical benefit from the drugs. The mechanisms that account for the lack of prolonged inhibition of viral replication by these agents are not fully understood. The activity of RT inhibitors might be potentiated by inhibiting host cellular enzymes essential for efficient HIV reverse transcription. Based on this information, comparisons of the antiviral effects of ddI monotherapy and hydroxyurea plus ddI, with the cellular enzyme ribonucleotide reductase as a potential target, should be done.