Steam addition effect on NO reduction in kerosene spray combustion was investigated experimentally. Three steam addition pathways (Case-1, Case-2 and Case-3) were arranged to find out the effective way of steam addition. In Case-1, steam was directly introduced into the fuel spray. In Case-2, it was pre-mixed with combustion air and introduced into the combustor. In Case-3, it was introduced through side holes of the combustor. NO, O(2), CO, CO(2), and temperature distributions in the combustor were analyzed for these steam pathways. It was clearly observed that the maximum temperature was reduced and high temperature region in the combustion chamber became narrow with steam addition. As a result, the effects of NO reduction in Case-1 and Case-2 were stronger than that in Case-3. It was considered that the suppression of NO formation in just after ignition region was necessary to reduce NO emission from the combustor. (C) 2010 Elsevier Ltd. All rights reserved.