In this retrospective study, we identified and reviewed the records of all patients with HIV seen for an initial screening examination for CMV retinitis at the Ocular Infectious Diseases Clinic, Chiang Mai University, Chiang Mai, Thailand, from July 6, 2006, to December 24, 2009. Collected data included diagnosis of CMV retinitis, age, sex, CD4 lymphocyte count, visual acuity, presence of HIV retinopathy, and treatment with antiretroviral drugs. We calculated the incidence of CMV retinitis in patients who initially had negative results on a screening examination, stratified by baseline characteristics. We used the Mantel-Haenszel rate ratio to assess for risk factors associated with incident CMV retinitis following negative results on an initial screening examination. Ethical approval was obtained from the Research Ethics Committee at Chiang Mai University and from the Committee for Human Research at the University of California, San Francisco.