Objective-To determine whether implementation of provider-initiated HIV counseling would increase the proportion of tuberculosis patients that received HIV counseling and testing. Design-Cluster-randomized trial with clinic as unit of randomizationSetting-Twenty, medium-sized primary care TB clinics in the Nelson Mandela Metropolitan Municipality, Port Elizabeth, Eastern Cape Province, South Africa Subjects-A total of 754 adults (≥ 18 years) newly registered as tuberculosis patients the twenty study clinics Intervention-Implementation of provider-initiated HIV counseling and testing. Main outcome measures-Percentage of TB patients HIV counseled and tested.Secondary-Percentage of patients HIV test positive and percentage of those that received cotrimoxazole and who were referred for HIV care.Results-A total of 754 adults newly registered as tuberculosis patients were enrolled. In clinics randomly assigned to implement provider-initiated HIV counseling and testing, 20.7% (73/352) patients were counseled versus 7.7% (31/402) in the control clinics (p = 0.011), and 20.2 % (n = 71) versus 6.5% (n = 26) underwent HIV testing (p = 0.009). Of those patients counseled, 97% in the intervention clinics accepted testing versus 79% in control clinics (p =0.12). The proportion of patients identified as HIV-infected in intervention clinics was 8.5% versus 2.5% in control clinics (p=0.044). Fewer than 40% of patients with a positive HIV test were prescribed cotrimoxazole or referred for HIV care in either study arm.Conclusions-Provider-initiated HIV counseling significantly increased the proportion of adult TB patients that received HIV counseling and testing, but the magnitude of the effect was small. Additional interventions to optimize HIV testing for TB patients urgently need to be evaluated.