The expression patterns of the genes involved in flavonoid biosynthesis and the chnges in anthocyanin content were investigated in small radish (Raphanus sativus L. var sativus) seedlings during light treatment. Anthocyanin content increased until day 4, reaching about 100-fold greater than the control plants, then decreased. CHS (chalcone synthase) mRNA reached a maximum level at 4 h, remained at relatively high levels until day 3, and then decreased rapidly. The CHI (chalcone isomerase) and DFR ( dihydrofolate reductase) mRNA levels reached maximum at 6 h and day 2, respectively, but were decreased rapidly thereafter. All the genes were expressed strongly in hypocotyls, but were either expressed weakly in roots or not expressed at all in cotyledons. Genomic hybridization showed that the CHS gene belonged to a small multigene family, which the CHI and DFR genes were present in one copy per haploid genome.