This paper studies the efficiency of U.S. multi-mode bus transit systems by asking whether they could expand their service (outputs) without requiring additional resources (inputs); or whether they could reduce input utilization without having to reduce service. A system which can do neither is said to be technically efficient . The technological possibilities facing the industry are identified by computing a piecewise-linear best-practice production frontier exhibiting variable returns to scale and weak disposal. The findings indicate that 80 percent of the bus systems studied are technically efficient, and that the extent of inefficiency in the industry is slight