Tuberculosis (TB) is a preventable and a treatable disease yet it is considered to be one of the most common infections seen in HIV. People who are infected with HIV are 20 times more likely to develop TB than those without HIV. Globally, there are nearly 40 million people living with HIV and at least one-third of them are infected with TB. Ontario accounts for the highest number of TB cases in Canada yet HIV-TB co-infection in Ontario is not well described. Despite the close relationship between TB and HIV and increasing efforts to fight both concurrently, TB continues to create economic and social burden in HIV infections. Our study estimates the prevalence of active and latent TB and identifies risk factors associated with TB in a cohort of individuals living with HIV in Ontario. Cases diagnosed with HIV during 2001 to 2009 were extracted from the Ontario HIV Treatment Network Cohort Study (OCS). Reviewing Mantoux test results, diagnoses and medication history, identified active and latent TB cases. Period prevalence was estimated by proportion with TB and multivariate analyses were performed to identify associated factors. One thousand two hundred and ninety-three cases (1293) met our selection criteria. Three hundred and eighty four (384; 29.7%) were 29 years or younger, 805 (62.3%) aged between 30 years and 50 years and 104 (8.0%) aged 50 years or older. One thousand and nine (1009; 78.0%) were males. Four hundred and sixty six (466; 36.0%) had at least one record of a Mantoux skin test. The prevalence of active TB was 76/1293 = 0.0587 or 5.87% (95% CI 4.6% to 7.0%) whereas the prevalence of latent TB varied from 5.26% (68/1293 = 0.0526) 95% (CI 4.0% - 6.5%) to 11.37% (53/466 = 0.1137) 95% CI (8.2% to 13.7%) depending on the methodology. In the multivariate analysis, factors associated with active TB were age and birthplace. Individuals 50 years and older were more likely to have active TB than individuals 30 years and younger (OR 4.3 CI (1.7-12.7), p <0.01). Individuals born in Africa were more likely to have active TB than Canadian born (OR 14; 95% CI (5.9 – 32.8) p < 0.001). Factors associated with latent TB were sex and birthplace. Females were more likely to have latent TB than males (OR 2.4; 95% CI (1.1 – 5.2) p < 0.05). Individuals born in Africa were more likely to have latent TB than Canadian born (OR 12.3; 95% CI (4.7 – 32.1) p < 0.001). TB remains a major problem in persons infected with HIV with rates disproportionally high among the foreign born population. Low rates of Mantoux tests in OCS present a missed opportunity for active TB prevention among individuals with HIV. To identify individuals with higher risk of having TB after HIV diagnosis, better screening tools to identify latent TB are needed. Consideration should be given to data capture systems that would ideally be linked between Public Health and HIV clinics. / UOIT