A cooperative cold-start and warmup driveability program was conducted by the Coordinating Research Council (CRC) in Yakima, Washington, during the fall of 1989. The program investigated the independent effects of front-end and mid-range volatility on cold-start and warmup driveability of twenty-four late model vehicles at intermediate ambient temperatures (30°F - 56°F). Volatility ranges investigated were those that may be required of future summertime fuels. Mid-range volatility (T50) was found to have a substantially significant impact on driveability, regardless of fuel-system type, while front-end volatility (RVP) was found to show a lesser but still significant effect on carbureted and throttle-body-injected vehicles. Oxygenate content/type was also a significant variable.