[영문]BACKGROUND:: Nonadherence with highly active antiretroviral therapy (HAART) is common in typical human immunodeficiency virus (HIV) patient care settings, but the consequences have not been well described. This study aimed to quantify the clinical and economic effects of nonadherence and estimate the cost-effectiveness of improving adherence in treatment-naive HIV patients. METHODS:: A Markov model was developed to project quality-adjusted life expectancy and direct medical costs for patients on an initial once-daily regimen of efavirenz, lamivudine, and stavudine XR. The model compared 2 adherence scenarios: “ideal” (based on clinical trials) and “typical” (based on observational studies in actual practice). Disease progression was a function of viral load, CD4 count, and adherence. Data on HIV natural history, treatment benefits, costs, and utilities were derived from the literature. RESULTS:: With typical adherence, patients lose 1.2 quality-adjusted life years (QALYs) that could be gained with ideal adherence. Improving adherence to ideal levels is cost-effective at