To quantify the risk of human immunodeficiency virus (HIV) infection in children with tuberculosis (TB) a hospital-based, 1-year prospective, case-control study was performed in Addis Ababa, Ethiopia. Children with TB were compared to a control group of children admitted for elective surgery. The control group was also compared to a recent census of the background population. The crude odds ratio for HIV infection was 8.6 (95 % CI 2.2-73). After adjustment for possible confounders in a multivariate regression model, the odds ratio for HIV infection in children with TB was found to be 12.7 (95% CI 2.9-55). Of several independent determinants of TB assessed in the study, this association was the strongest. Until HIV transmission has reached its peak, an increasing burden of dual infection among Ethiopian children is to be expected.