This retrospective study on the impact of diabetes on the course of pulmonary tuberculosis was conducted in 32 diabetic patients with tuberculosis treated at the Brazzaville University Hospital between January 1994 and December 1998. This group was compared with a control group of 100 non-diabetic patients with tuberculosis. HIV-positive patients were excluded from the study. Diabetes appeared to have an induction and aggravating effect on tuberculosis. Tuberculosis is more frequent in diabetics than in non-diabetics. Radiological signs of tuberculosis are more pronounced in diabetics. Treatment failure and death are also more frequent. Tuberculosis aggravates diabetes and increases the frequency of complications compared with diabetics without tuberculosis.