Leaf chlorophyll content (LCC) is an important physiological character, being closely related to photosynthetic ability in rice. In this study, 182 recombinant inbred (RI) lines derived from a backcross of Koshihikari (japonica)/Kasalath (indica)//Koshihikari, kindly provided by the National Institute of Agrobiological Resources, Japan, were used to identify quantitative trait loci (QTLs) for LCC at the maximum tillering stage of rice. The seeds of 182 RI lines, along with those of both parents, Koshihikari and Kasalath, were sown on 10 April 2004. After 30 d, seedlings were transplanted to the experiment farm of Miyazaki University, using a single seedling per hill and 10 × 15-cm spacing. The recommended cultural practices were followed. At maximum tillering stage, 30 newly developed and healthy leaves for each line were selected for LCC measurement with two replicates using a chlorophyll meter (SPAD-502, Minolta Co., Ltd., Japan). Average values for each line and a subset of 162 restriction fragment length polymorphism (RFLP) markers (www.rgrc.dna.affrc.go.jp/jp/ data/KK-BIL182-20030506.xls)were used for QTL statistical analysis. The QTL analysis was performed by Windows QTL Cartographer software version 2 (Wang et al 2003) through the composite interval mapping method. A locus with LOD >2.0 was to be declared a putative QTL. In addition, the additive effects effects and the percentage of variation explained by an individual QTL were also estimated.