In preparation for a proposed intervention at an antiretroviral therapy (ART) clinic in Durban, South Africa, we explored the dynamics and patterns of cellular phone use among this population, in order to ascertain whether clinic contact via patients' cellular phones was a feasible and acceptable modality for appointment reminders and adherence messages. Adults, who were more than 18 years old, ambulatory, and who presented for treatment at the clinic between October-December 2007, were consecutively recruited until the sample size was reached (n = 300). A structured questionnaire was administered, including questions surrounding sociodemographics, cellular phone availability, patterns of use, and acceptability of clinic contact for the purpose of clinic appointment reminders and adherence support. Most respondents (n = 242; 81%) reported current ownership of a cellular phone with 95% utilizing a prepaid airtime service. Those participants who currently owned a cellular phone reported high cellular phone turnover due to theft or loss (n = 94, 39%) and/or damage (n = 68, 28%). More females than men switched their cell phones off during the day (p = 0.002) and were more likely to not take calls in certain social milieus (p ≤ 0.0001). Females were more likely to share their cell phone with others (p = 0.002) or leave it in a place where someone could access it (p = 0.005). Most respondents were willing to have clinic contact via their cellular phones, either verbally (99%) or via text messages (96%). The use of cellular phones for intervention purposes is feasible and should be further investigated. The findings highlight the value of gender-based analyses in informing interventions.