BACKGROUND: Several factors associated with human virologic failure in patients with immunodeficiency virus (HIV) infection are low CD4+ cell counts, advanced clinical stage, poor subscribing, subtherapeutic drug levels, etc. Among these factors, poor adherence is one of the leading causes. MATERIALS AND METHODS: We evaluated the adherence to antiretroviral treatment in HIV infected Koreans using questionnaire. We evaluated the factors associated with poor adherence and analyzed the correlation between the adherence to antiretroviral treatment and virologic failure. RESULTS: A total of 49 patients responded to the questionnaire. Of the 49 patients, 26 (53.1%) answered that they had never forgotten to take their medicine, and 23 (46.9%) answered that they had taken all their medications during the last week. The reasons for missed doses were forgetting, being too busy, having adverse side effects, etc. Low CD4+ T cell counts, longer duration of antiretroviral treatment, and longer duration of being diagnosed with HIV infection were associated with poor adherence in HIV infected Koreans (P<0.05). There was correlation between poor adherence and virologic failure in these HIV-infected Koreans (P<0.05). CONCLUSION: Because poor adherence induces treatment failure, monitoring adherence is very important for successful antiretroviral treatment. Questionnaire was a good method for monitoring adherence in HIV infected patients.