During a 1-7 year follow-up of 1250 African diabetic patients at Muhimbili Medical Centre, Dar es Salaam, 68 (5.4%) were known to have developed pulmonary tuberculosis and two (0.2%) spinal tuberculosis. In 18 (25.7%) of the 70 patients tuberculosis was diagnosed prior to the diagnosis of diabetes, and in 32 (45.7%) after the diagnosis of diabetes. In 20 (28.6%) patients tuberculosis and diabetes were diagnosed at approximately the same time with most presenting with symptoms of diabetes. The prevalence of tuberculosis was greater in the young, in those with a low body mass index (BMI), in patients with insulin-dependent diabetes mellitus compared to those with non-insulin-dependent diabetes mellitus (9.0% vs 2.7%) and in those whose diabetes was poorly controlled. Seventeen (24.3%) of the 70 patients are known to have died. Pulmonary tuberculosis may progress rapidly and a high index of suspicion is required. It remains a significant cause of morbidity and mortality among diabetic patients in developing countries.