In-use fuel economy was evaluated for two of the hybrid school buses, which were deployed in two different school districts in Iowa. Each school district selected a control bus, which runs on a route similar to the hybrid school bus and odometer readings, amount of fuel, and maintenance were recorded for each bus. The buses were deployed in 2008. The Nevada School district uses a 20 biodiesel blend. The same fuel was used in the hybrid and control bus. Fuel consumption was calculated for each school district and fuel consumption data were compared for the hybrid and control bus using a Wilcoxon Signed Rank test. Fuel economy for the hybrid bus in Nevada was 30% better than for the control bus and fuel economy for the hybrid bus in Sigourney was 36% higher than for the control bus. Both differences were statistically significant. Although the buses demonstrated superior fuel economy over conventional buses, a number of maintenance problems occurred. This is an abstract of a paper presented at the 103rd Air and Waste Management Association Annual Conference and Exhibition (Calgary, Alberta, Canada 6/22-25/2010).