['Recent tobacco smoking has been identified as a risk factor for developing tuberculosis, and two studies which have investigated its association with relapse of tuberculosis after completion of treatment had conflicting results (and did not control for confounding). The objective of this study was to investigate risk factors for tuberculosis relapse, with emphasis on smoking.', 'A cohort of newly diagnosed TB cases was followed up from their discharge after completion of treatment (in 2001-2003) until October 2006 and relapses of tuberculosis ascertained during that period. A case of relapse was defined as a patient who started a second treatment during the follow up.', 'Smoking (OR 2.53, 95% CI 1.23-5.21) and living in an area where the family health program was not implemented (OR 3.61, 95% CI 1.46-8.93) were found to be independently associated with relapse of tuberculosis.'] Does smoking increase the risk of relapse after successful tuberculosis treatment?