Direct sputum smear microscopy is the most widely used means for the diagnosis of pulmonary tuberculosis (TB) and is available in most primary health-care laboratories at health-centre level. Smear microscopy may, however, be costly and inconvenient for patients, who have to make multiple visits to health facilities to submit multiple sputum specimens over several days. A number of TB control programmes have found high rates of initial patient default as a result, with high mortality recorded in several resource-limited settings. It has been shown conclusively that good quality microscopy of two consecutive sputum specimens identifies the vast majority (95–98%) of smear-positive TB patients. Conventional case-finding approaches usually involve microscopic examination of 'spot-morning' sputum specimens (in countries with a two-specimen system) or examination of 'spot-morning-spot' sputa (in those with a three-specimen approach). The majority of sputum results are therefore available only on the second or third day after the patient presents to a health service. In 2009, the strength of the evidence for a 'same-day diagnosis' approach (microscopy of two consecutive sputum specimens on the same day) was assessed by the World Health Organization (WHO), following standards appropriate for evaluating both the accuracy and the effect of new interventions on patients and public health. It was found that there was sufficient generalizable evidence that a same-day diagnosis approach is equivalent, in terms of diagnostic accuracy, to conventional microscopy case-finding strategies. Neveretheless, significant organizational and programme changes would be required to optimize the advantages of sameday diagnosis, to ensure that laboratory results are received back at the health facility and that patients start treatment on the same day. In addition, there is currently no evidence that early diagnosis of TB results in better uptake of treatment or improved treatment outcomes, so that programmes must closely monitor the effect of revised case-finding strategies. On the basis of these findings, WHO recommends that countries that have successfully implemented current WHO policy for a two-specimen case-finding strategy consider switching to same-day diagnosis, especially in settings where patients are likely to default from the diagnostic process. Countries that are still using the three-specimen case-finding strategy should consider a gradual change to same-day diagnosis, once WHO-recommended external microscopy quality assurance systems are in place and good-quality microscopy results have been documented. It is essential that programmatic, logistic and operational implications at country level be taken into account in implementation of same-day diagnosis.