Objectives: To examine rates of culture proved tuberculosis in HIV infected patients in three specialist centres in north central London. Methods: Cases of tuberculosis in patients with previously documented HIV infection from 1990 to 1996 were identified retrospectively from microbiological/clinical records at Chelsea and Westminster, St Mary's, and University College London Hospitals. Results: Between 1990 and 1996 202 cases of culture proved tuberculosis were identified at the three centres. Of these, 132/202 (65.3%) occurred in homosexual/bisexual men, 41/202 (20.3%) were in patients with heterosexual contact in sub-Saharan Africa, and 29/202 (14.4%) were in 'others.' Overall 148/202 (73.3%) had pulmonary tuberculosis. The total number of HIV infected individuals seen at the three centres increased from 4298 in 1990 to 5048 in 1996. Rates of tuberculosis in the three centres increased from 0.46% in 1990 to 0.83% in 1996. Part of this increase was due to an increase in tuberculosis among Africans from 1993 to 1996. Conclusions: Rates of HIV associated tuberculosis increased in these three centres in north central London between 1990 and 1996. In part this was due to an increase in the number of African patients with HIV infection attending the three centres. In addition, there was circumstantial evidence of recent transmission among homosexual men with HIV infection. Prospective 'real time' surveillance of tuberculosis in HIV infected patients is needed in order to detect case clustering and to improve tuberculosis control.