A DNA fragment representing a transcriptionally active retrotransposon of Ty3-gypsy type was isolated and characterized from rice (Oryza sativa L.). The fragment (named RIRE9) includes the coding sequences for the C-terminal part of the RNase H domain and the N-terminal part of the integrase domain in the polyprotein region. Northern blot hybridization indicated that this element was expressed in rice leaves and stems, suggesting that it is potentially active to transpose under normal growth conditions. Using dot-blot hybridization, the copy number of RIRE9 was estimated to be about 1600 copies per haploid rice genome. Five homologous copies of RIRE9 were assigned to five distinct positions of four chromosomes by restriction fragment length polymorphism (RFLP) mapping approach using an indica-japonica rice doubled-haploid (DH) population and its molecular linkage map.