Despite China's free antiretroviral therapy (ART) program, there are high rates of treatment failure, large sociodemographic disparities in care outcomes and emerging medication resistance. Understanding patient medication adherence behaviors and challenges could inform adherence interventions to maximize the individual and prevention benefits of ART. This study assessed recent nonadherence and treatment interruption among 813 HIV-infected adult outpatients in Guangzhou, China. Participants completed a behavioral survey, underwent chart review, and were tested for syphilis, gonorrhea, and chlamydia. Factors associated with suboptimal adherence were identified using univariate and multivariate logistic regression. Among 721 HIV-infected adults receiving ART, 18.9% reported recent nonadherence (any missed ART in the past four weeks) and 6.8% reported treatment interruption (four or more weeks of missed ART in the past year). Lower education, living alone, alcohol use, and being on ART one to three years were associated with recent nonadherence. Male gender, lower education, and being on ART one to three years were associated with treatment interruption. ART medication adherence interventions are needed in China that include individualized, long-term adherence plans sensitive to patients' educational and economic situations. These interventions should also consider possible gender disparities in treatment outcomes and address the use of alcohol during ART. Successful ART medication adherence interventions in China can inform other international settings that face similar adherence challenges and disparities.