The successful treatment of people living with HIV and the monitoring and evaluation of antiretroviral therapy (ART) programs both depend on regular and complete follow-up. Analyses restricted to clients remaining in care will underestimate mortality among all clients who started ART. Biased estimates of program-level mortality hamper the evaluation of single programs and the comparison between programs, settings and countries. We publish here a standardized protocol used to trace people living with HIV classified as lost to follow-up at ART programs members of the International Epidemiology Databases to Evaluate AIDS in Southern Africa (IeDEA-SA), and to determine their vital and care status.