Adrenal glands may be involved during both acute and chronic tuberculosis. They are enlarged in acute pulmonary tuberculosis. We aimed to investigate the changes in adrenal size in acute pulmonary tuberculosis before and after therapy in a prospective study. Eleven hospitalized patients with newly diagnosed sputum positive pulmonary tuberculosis were studied. Basal cortisol levels were measured in the patients before and after the therapy. Cortisol levels were also measured 30 and 60 min after Synacthen (250 mu g i.v.) injection in the patients before the therapy. The size of the adrenal glands was measured by computerized tomography. The maximum width perpendicular to the long axis of the body of the gland, maximum width of the medial and lateral limbs and the length of the adrenals were measured. All measurements were done before and after the eight-month anti-tuberculosis therapy. All 11 patients had an intact adrenal cortisol reserve. Both the width and length of the right and left adrenal glands were significantly greater before the therapy than after the therapy. We conclude that adrenal enlargement demonstrated by computerized tomography in acute pulmonary tuberculosis is reduced after appropriate therapy.