In this paper, the combustion and emission characteristics of a direct injection diesel engine operating on diesel-propane blends were investigated. The results showed that under the same operating condition, the effective thermal efficiency increased with the increase of propane proportion in the blends. Ignition delay and combustion durations of diesel-propane blends were decreased with the increase of propane proportion in the blends. Maximum cylinder pressure, maximum rate of pressure rise, maximum rate of heat release and maximum mean combustion temperature of the diesel-propane blends increased with the increase of propane proportion in the blends. Simultaneous reduction in exhaust CO, HC and smoke emissions could be realized when operating on the diesel-propane blends. Exhaust NO, emission gave an increasing trend when operating on the diesel-propane blends. (C) 2007 Elsevier Ltd. All rights reserved.