Ballard Power Systems Inc. and SAIC Canada have built the world's first Zero Emission Vehicle (ZEV) bus powered by Proton Exchange Membrane (PEM) fuel cells. The 32-foot transit bus demonstrates that PEM fuel cells can provide the same performance as a diesel engine but with no harmful emissions. Phase 1 of the commercialization program began in November 1990 and was completed in March 1993. A detailed description of the bus configuration along with operating results to date will be reported. The overall plan to achieve commercialization of 40-foot PEM fuel cell ZEV buses by 1998 will be described.