Corticosteroids are beneficial in the treatment of some forms of tuberculosis, but their role in TB affecting HIV-positive patients is not clear. During a cohort study of tuberculosis patients in Lusaka, Zambia, prednisolone was prescribed for specific indications. Six of 47 (13 per cent) of patients who received prednisolone early in treatment developed herpes zoster, compared with 2 of 118 (2 per cent) of those who did not. Three patients who received prednisolone developed Kaposi's sarcoma, compared with none who did not. At 2 months patients who had received prednisolone showed a greater improvement in generalized lymphadenopathy and cough. Controlled studies of the risks and benefits of administration of corticosteroids to HIV-positive TB patients are urgently needed.