We performed a sequential follow-up of oral glucose tolerance tests on 54 Nigerian patients with active pulmonary tuberculosis in order to determine the significance of glucose intolerance in tuberculosis. Twenty-three patients (42.6%) were found to have abnormal results, including three (5.6%) with a diabetic pattern and 20 (37.0%) with impaired glucose tolerance; 15 (75%) of the latter group had normal results after 3 months treatment while one each of the former group was diabetic, intolerant of glucose and normal respectively. Two patients with normal results initially had impaired glucose tolerance at the second test. Three months after full anti-tuberculosis medication, only one of the eight patients with impaired glucose tolerance at the second oral glucose tolerance test remained intolerant of glucose. Only one patient was frankly diabetic. Our results suggest that glucose intolerance in pulmonary tuberculosis is secondary to infection and is reversible.