Objective: Telomere length is a marker of biological aging that has been linked to cardiovascular disease risk. The black South African population is witnessing a tremendous increase in the prevalence of cardiovascular disease, part of which might be explained through urbanization. We compared telomere length between black South Africans and white South Africans and examined which biological and psychosocial variables played a role in ethnic difference in telomere length. Methods: We measured leukocyte telomere length in 161 black South African teachers and 180 white South African teachers aged 23 to 66 years without a history of atherothrombotic vascular disease. Age, sex, years having lived in the area, human immunodeficiency virus (HIV) infection, hypertension, body mass index, dyslipidemia, hemoglobin A1c, C–reactive protein, smoking, physical activity, alcohol abuse, depressive symptoms, psychological distress, and work” “stress were considered as covariates. Results: Black participants had shorter (median, interquartile range) relative telomere length (0.79, 0.70Y0.95) than did white participants (1.06, 0.87Y1.21; p G .001), and this difference changed very little after adjusting for covariates. In fully adjusted models, age (p G .001), male sex (p = .011), and HIV positive status (p = .023) were associated with shorter telomere length. Ethnicity did not significantly interact with any covariates in determining telomere length, including psychosocial characteristics.” “Conclusions: Black South Africans showed markedly shorter telomeres than did white South African counterparts. Age, male sex, and HIVstatuswere associatedwith shorter telomere length.No interactions between ethnicity and biomedical or psychosocial factorswere found. Ethnic difference in telomere length might primarily be explained by genetic factors. Key words: cardiovascular disease, ethnicity, genetics,” “psychological stress, telomere.