While medication adherence is critical to successful treatment of HIV, there are few studies of interventions demonstrating improvements in adherence. This may be a particular challenge in the developing world, which has a larger burden of HIV but fewer resources than industrialized countries. The investigators propose a randomized controlled trial of cellular phone text message reminders to improve medication adherence. Our pilot study will be set in a large HIV clinic in Gaborone, Botswana, where Penn researchers have collaborated on research projects in the past. The primary study outcome will be antiretroviral medication adherence.