The Rice Expression Profile Database (RiceXPro) is a repository of gene expression data derived from microarray experiments encompassing the entire life cycle of the rice plant from germination, seedling, tillering, stem elongation, panicle initiation, booting, heading, flowering, and ripening stage. This database is part of a project on rice gene expression profiling which aims to characterize the function of all predicted genes in rice using an oligonucleotide microarray platform based on the manually curated gene models in RAP-DB and rice full-length cDNA sequence (KOME) information. The project is supported by a grant from the Genomics for Agricultural Innovation of the Ministry of Agriculture, Forestry and Fisheries of Japan.