Variations in swollen hypocotyl of red and white radish (Raphanus sativus) varieties are attributed to the level of anthocyanin accumulation. However, it is not known which genes in the biosynthetic pathway are involved in this variation. Upon treatment with exogenous sucrose, hypocotyl of red radish produced a large amount of anthocyanins, while that of white radish produced little. Six genes involved in anthocyanin production and one gene in lignin biosynthesis in red and white varieties were tested to demonstrate which genes were expressed on addition of sucrose. In red radish, transcripts of all six anthocyanin-related genes were remarkably induced by sucrose, while none of them were induced in white radish. Transcripts for cinnamoyl-CoA reductase involved in lignin biosynthesis were not influenced by sucrose in either variety. These results suggest that the low level of anthocyanin accumulation in white radish is due to the weak response of anthocyanin-related genes to sucrose.