BACKGROUND: Lay or community health workers (LHWs) are an important human resource in primary health care, and contribute to improving access to care. However, optimal use of LHWs within the health system is often hampered by a poor understanding of how this cadre organizes its work. This study aimed to better understand how LHWs organize and structure their time in providing treatment and adherence support to people on TB treatment and/or antiretroviral therapy (ART) in South Africa. METHODS: Fourteen LHWs participated across three low-income peri-urban communities in Cape Town. Each LHW was observed by a researcher for one day, and data collected on each activity and the time spent on it. Data were summarized in the following categories: travel to the patient's home, waiting time and patient contact time. RESULTS: Ninety-seven attempted visits to patients were observed, and patients were located in 69 of these. On average, LHWs conducted six visits per day, each lasting an average of nine minutes. Forty-six percent of the observed time was spent with patients, with the balance spent on 'non-contact' activities, including walking to and waiting for patients. The average walking time between patients was 8 minutes (range: 3 to 15 minutes). Activities during visits comprised medical care (that is ensuring that medication was being taken correctly and that patients were not experiencing side-effects) and social support. Other tasks included conducting home assessments to determine risks to treatment adherence, and tracing patients who had defaulted from treatment. CONCLUSIONS: Because of their tasks and working environment, LHWs providing support to people on TB treatment and ART in South Africa spend a substantial proportion of their time on 'non-contact' activities. Programme managers need to take this into account when developing job descriptions and determining patient case-loads for this cadre. More research is also needed to explore whether these findings apply to other tasks and settings. Strategies should be explored to mitigate the challenges that LHWs experience in locating and supporting patients, including the use of new technologies, such as mobile phones.