Emissions Iron the two methanol-powered buses used in the California Methanol Bus Demonstration have been characterized. The M.A.N. SU 240 bus is powered by M.A.N.'s D2566 FMUH. methanol engine, and utilises catalytic exhaust af tertreatment. The GMC RTS II 04 bus is powered by a first-generation DDAD 6V-92TA methanol engine without exhaust aftertreatment. Emissions of HC, CO, NOx, unburned methanol, aldehydes, total particulates, and the soluble fraction of particulate were determined for both buses over steady-state and transient chassis dynamometer test cycles. Emission levels from the M.A.N. bus were considerably lower than those from the GMC bus, with the exception of NOx, Comparison of emission levels fro n methanol-and diesel-powered buses indicates that substantial reductions in emissions are possible with careful implementation of methanol fueling.