A brief description is provided of COMDIS Public Private Partnerships (PPP) research to address the issue that in some low-income countries private medical practitioners (PPs) are the providers of choice for the majority of urban residents with chest complaints, despite the poor quality of tuberculosis (TB) diagnosis, treatment and reporting that they provide. The work started with a pilot project in Lalitpur, Nepal, commencing in 1997. Five Direct Observation of Treatment (DOT) centres were opened in locations convenient for patients. The Nepal National Tuberculosis Programme (NTP) provided free TB drugs to the centres. PPs referred patients to the centres, and were kept informed of patients’ progress. Patients who missed one or more days DOT were traced by NGO volunteers who encouraged them to continue with their treatment. Patients were referred back to the referring PP at the end of treatment, and for non TB-related illnesses. The Lalitpur PPP proved to be very successful: treatment outcomes exceeded international targets, case notification doubled, and costs per patient cured were similar to those in the public sector. Responsibility for the PPP was transferred to the municipality in 2002, and it has been maintained without external support. A much more ambitious project was then developed in Bangladesh. Operational research in Dhaka demonstrated its feasibility and effectiveness; ongoing work will determine its sustainability. In Pakistan, all provinces have now approved PPP as a policy option for TB control. COMDIS-led operational research has led to development of detailed guidelines and tools.