['This study was conducted in two districts in India where DOTS has been implemented. There are 39 microscopy centres in Anantpur district and 34 in Nellore district (one per 100,000 population), each with a trained microscopist. Periodic follow-up sputum microscopy is performed for all tuberculosis (TB) patients on treatment, with two sputum specimens examined on each follow-up. Results are recorded in a laboratory register.', 'To determine whether examining two sputum specimens for follow-up is useful for assessing treatment outcome.', 'A retrospective study using data from laboratory registers of all microscopy centres for 2002 in Anantpur and 2003 (January-June) in Nellore.', 'Of 5086 follow-up examinations done in Anantpur and 1028 in Nellore, 8% were acid-fast bacilli positive. One additional positive result was obtained on examination of a second sputum specimen. This result did not significantly add to the assessment of treatment outcome.'] Is repeated sputum microscopy essential for monitoring tuberculosis treatment response?