Maintaining greater than 95% adherence to antiretroviral medication is necessary in order to have the greatest therapeutic impact on HIV infection. Furthermore, evidence suggests that adherence rates of between 70% and 89% are significantly associated with viral rebound and the development of drug resistance. Adherence rates at and above the 95% level are difficult for patients to achieve and maintain. Our aim was to determine if an adherence intervention could improve adherence among patients attending an ambulatory care clinic at a large public hospital. The intervention was delivered by a multidisciplinary team of health care professionals and consisted of education coupled with the provision of devices designed to assist patient memory and adherence. A crucial component of the intervention consisted of the identification of patient specific barriers to adherence and the development of strategies to circumvent these problems. Adherence was assessed using patient self-report over the past 4, 7, and 28 days and by calculation of the Morisky score. The study was conducted as a randomised controlled trial using the stepped wedge design with a total of 68 subjects randomised to receive the intervention over a 20-week period. Adherence before and after the intervention formed the analysis. There was a significant decrease in the number of missed doses over the past 4 (1.9 to 1.0, p < 0.001), 7 (3.0 to 1.8, p < 0.001) and 28 (7.4 to 4.2, p < 0.001) days and a decrease in the Morisky score, indicating an improvement in medication taking behaviour (1.3 to 0.5 p < 0.001).