Short delays to treatment are important for the control of tuberculosis (TB). National Tuberculosis Programmes provide free diagnosis and treatment for smear-positive patients, so that the patients' out-of-pocket medical expenditure could be almost nil. The factors associated with delays in starting treatment, and the pre-treatment out-of-pocket medical expenditure for TB patients, have now been investigated in the Bolivian city of Cochabamba. Bolivia is the Latin American country with the highest incidence of TB. It is covered by a national TB programme that provides free diagnosis and free treatment for smear-positive patients. Structured interviews with 144 smear-positive patients enrolled in this programme revealed median patient, provider and total delays of 3.6, 6.2 and 12.9 weeks, respectively. The total delays were longer for the female patients than for the male, and for patients who consulted private doctors than for the other patients. When the first healthcare provider was a doctor, the median provider delay was 4.9 weeks in the public sector but 7.2 weeks in the private. The median out-of-pocket medical expenditure per patient, which was U.S.$13.2 overall, was much higher for those who consulted a private doctor than for those who did not (U.S.$21.9 v. U.S.$5.4, respectively; P<0.001). It appears that interventions targeting doctors (in both the private and public sectors) are likely to have a larger impact on the shortening of delays in TB treatment than interventions targeting patients. They could also reduce unnecessary out-of-pocket expenditure.