Jatropha oil which is a large, branched triglycerides type vegetable oil has good potential as an alternative diesel fuel. Its combustion characteristics have been observed experimentally by igniting the oil droplet of various diameters and temperatures on a junction of a thermocouple. The combustion characteristics are identified from flame image and temperature signal in the center of the droplet. The results show that the jatropha oil droplet performs two steps combustion. Fatty acid burned in the first step and glycerol does in the second step. The onset of micro-explosion occurs shortly before the second step combustion and it becomes more frequent as the oil temperature is increased. (C) 2009 Elsevier Ltd. All rights reserved.