Tiller angle of rice is an important agronomic trait that contributes to breed new varieties with ideal archi-tecture. In this study, we report mapping and characteriza-tion of a rice mutant defective in tiller angle. At the seedling stage, the newly developed tillers of the mutant plants grow with a large angle that leads to a lazy phenotype at the mature stage. Genetic analysis indicates that this tiller- spreading phenotype is controlled by one recessive gene that is allelic to a reported mutant la. Therefore, the mutant was named la-2 and la renamed la-1. To map and clone LA, we constructed a large mapping population. Genetic linkage analysis showed that the LA gene is located between 2 SSR markers RM202 and RM229. By using the 6 newly-developed molecular markers, the LA gene was placed within a 0.4 cM interval on chromosome 11, allowing us to clone LA and study the mechanism that controls rice tiller angle at the molecular level. At this seedling stage, the newly developed tillers of the mutant plants grow with a large angle that leads to a lazy phenotype at the mature stage. Genetic, analysis that that tiller-spreading phenotype is controlled by one recessive gene that is allelic to a reported mutant la. la-2 and la renamed la-1. To map and clone LA, we constructed a large mapping population. Genetic linkage analysis showed that the LA gene is located between 2 SSR markers RM202 and RM229. By using the 6 newly-developed molecular markers , the LA gene was placed within a 0.4 cM interval on chromosome 11, allowing us to clone LA and study the mechanism that controls rice tiller angle at the molecular level.