This paper presents the results of experimental work carried out to evaluate the exhaust emissions characteristics of ordinary Malaysian coconut oil (COCO) blended with conventional diesel oil (OD) fueled in a diesel engine. This project complies with Malaysian Government strategy on biofuel research activity. The results showed that the addition of 30% COCO with OD produced higher brake power and net heat release rate with a net reduction in exhaust emissions such as HC, NOx, CO, smoke and polycyclic aromatic hydrocarbon (PAH). Above 30% COCO blends, such as 40 and 50% COCO blends, developed lower brake power and net heat release rate were noted due to the fuels lower calorific value; nevertheless, reduced emissions were still noted. (C) 2003 Elsevier Ltd. All rights reserved.