TransMilenio is a bus rapid transit system in Bogotá, Columbia resulting from a successful public-private partnership. The system comprises specialized infrastructure including exclusive lanes for high capacity articulated buses, efficient private operation, advanced fare collection system, and a new public authority for planning, developing and controlling the system. TransMilenio started operations in December 2000. By April 2002 it moved 650,000 pass/day in 38 Km bus ways, 62 stations, 470 articulated buses and 300 feeder buses operating 125 Km routes. Extensions will continue in the next 16 years to cover 85% of the daily trips in the city. TransMilenio is a high quality and sustainable transport solution, at a very low cost for the tax payers and the direct users. This paper presents the situation of Bogotá, the overall mobility strategy in which the mass transit system is embedded, the components of TransMilenio, the implementation strategy, and the results after five months of operation.