Since the beginning of the AIDS epidemic over thirty years ago, human immunodeficiency virus type 1 (HIV-1) has infected seventy-five million people and has claimed the lives of over thirty-six million people worldwide, making HIV/AIDS one of the most devastating global infectious disease epidemics in history. To date, no preventative vaccine or curative treatment exists for HIV-1 infection. The availability of drugs to treat HIV-1 infection has led to drug resistance, which limits the utility of antiviral therapy. This has provided the basis for the continual need for identifying new targets for antiviral drugs. This dissertation investigated the antiretroviral activity and mechanism of action for clofarabine, a purine nucleoside antimetabolite. Clofarabine was demonstrated to exert antiretroviral activity against both HIV-1 and human immunodeficiency virus type 2 (HIV-2). Studies directed at elucidating the antiretroviral mechanism of action support a model in which clofarabine acts as an inhibitor of ribonucleotide reductase, leading to imbalances in cellular dNTP pools, which reduces viral infectivity through an increase in the HIV-1 mutation rate.