Crosses between satsuma mandarins and tetraploid ponkan were made to produce triploid hybrid cultivars. Triploid embryos were obtained from the crosses using three seed parents, 'Ootsu No. 4', 'Aoshima' and 'Imamura', which produced comparatively small numbers of embryo per seed. Of the three, the frequency of triploid embryo production per fruit was highest in 'A oshima'. The frequency of triploid embryo production per seed in undeveloped seeds was higher than that in fully developed seeds. By the embryo rescue technique, triploid