Increasing frequency of treatment failures on potent antiretroviral therapy has accelerated the need for new classes of agents. Hydroxyurea, an agent broadly used for its antineoplastic properties, has been shown to inhibit HIV-1 in vitro and in vivo when combined with the nucleoside analogue reverse transcriptase inhibitor didanosine (ddI). There is an urgent need to prospectively test the safety, tolerability, and efficacy of hydroxyurea in late-stage, treatment-experienced patients.