BACKGROUND: Globally, Public-Private Mix (PPM) models of service delivery are recommended as a strategy for improving tuberculosis (TB) control. Several models of PPM-DOTS have been initiated under the Revised National TB Control Programme (RNTCP) in India, but scaling up and sustaining successful projects has remained a challenge. AIM: This paper examines factors accounting for the sustainability of a PPM-DOTS initiated in 1998 in Pimpri Chinchwad (PC), a city in Maharashtra, India. METHODS: A two-year intervention research project documented the workings of the PPM-DOTS programme. This paper draws on in-depth interviews with programme officers and staff, and semi-structured interviews with private practitioners (PP) practising in the study area. RESULTS: PPM-DOTS was originally introduced in PC, in order to increase access to DOTS. Over the years it has become an integral part of the RNTCP. Multiple approaches were employed to involve and sustain private providers' participation in PPM-DOTS. Systems were developed for supervision and monitoring DOTS in the private sector. Systematic use of operations research and successful mobilisation of available local resources helped set future direction for expanding and strengthening the PPM. The private sector's contribution to case detection and treatment success has increased, however ensuring referrals of TB suspects from all private providers continues to present a challenge. CONCLUSION: PPM-DOTS in PC is one of the few Indian models implemented as envisaged by global and national policy makers. Its successful operation for over a decade reiterates the importance of public sector initiative and leadership and makes it an interesting case for study and replication.