This paper gives a description of the Bay Area Rapid Transit (BART) system in San Francisco. The design and construction of the system depended upon the geography of the area and upon the equipment and skills of the many contractors involved-all of which are described. Details are given of the excavation for tunnels and stations and the equipment used in these operations. The design of the vehicles on the BART system was aimed toward passenger safety and comfort, and some details of the cars are shown. BART may be a model for rapid-transit development in communities where mass-transit systems will help solve urban transportation problems.