To investigate the combustion characteristics of Jatropha pure oil (JPO) and Jatropha methyl ester (JME) as an alternative fuels for gas turbines, combustion experiments were conducted at atmospheric pressure employing an air-assist pressure swirl atomizer. As well as the NOx and CO concentrations and smoke number in the exhaust gas, the flame radiation intensity was measured using the two-color method. The results show that the flame radiation intensity and the soot emission decrease with increasing mixing ratio of JPO or JME to diesel fuel. It was also found that the flame radiation intensity has a strong correlation with the mean diameter of the fuel spray for all fuels. The CO emission for JPO is higher than those for JME and diesel fuel in the case of low flame temperature. (C) 2014 Elsevier Ltd. All rights reserved.