Systemic endopolyploidy during development of radish (Raphanus sativus L.) is described. Flow cytometric measurements of relative nuclear DNA contents revealed that a majority of somatic cells in radish plants undergoes several rounds of endoreduplication, resulting in tissues that contain cells with multiple ploidy levels (also called ‘endopolyploidy’ or ‘polysomaty’). The distribution of endopolyploid cells is organ-specific. Endopolyploidy was not present in the embryos in dry seeds. Rapid and extensive endoreduplication occurred in the radicle and the hypocotyl of the embryos during germination of seeds. Endoreduplication events were detected in all tissues except shoot tip tissues. In vitro grown plants contained cells with five ploidy levels that correspond to 2C, 4C, 8C, 16C and 32C. Tuberous root tissues of in vivo grown plants also showed highly polysomatic nature. It is probably that growth of radish plants does not depend on cell proliferation alone. Under normal developmental programs, most somatic cells undergo a transition from proliferating state to endoreduplicating state. The biological significance of endoreduplication in radish plants is discussed.