Patient motivation is important in managing medication regimens such as antiretroviral treatment for HIV/AIDS. We tested whether self-determination theory could predict adherence behavior among 115 HIV-positive patients in the China Adherence through Technology Study, a randomized controlled trial of an intervention using text reminders and supportive counseling to increase adherence. Being in the treatment group had a significant effect on improving adherence; however, we did not find evidence that self-determination theory predicts adherence in this population of HIV-positive patients. Autonomous motivation was strongly associated with perceived competence; among low adherers, external regulation was negatively correlated with adherence.