In this paper the author report the results of breeding process and observat.ions on the induced autotetraploid soybean by the dropping method with colchicine lanolin mixture: 4 varieties belonging to two ecdlogical types, that is surnmer and autumn types were tested. The reasaent of 0.2and 0.4% was dropiped on the ' growing p, aint of young soybcan plants just after the ovate leaves had opened by spait twice a day during one dr two days. Stopped their growth for a time, but soon after dark green irrogular shaped or teratol-ogical foliages appeared Although many of th' trea-ted plants died out, 5 seeds for surnmer type and 214 seeds for autumn type were harvested. In the next generation 19 tetraploid plants belong-ing to two autumn varieties were confrro, ed by the size of pollen grains and other morphological characters. This number of palyploid plants correspond to 30% for the reared lines and 13% for the sowed 'seeds. In the second generation, 18 Iines out of 19 were confirmed to be tetraploid by chromosome counting and other morphological characters. The chromosome number at diakinesis and first metaphase varied from 26 to 40 according ?? o the ' number of teiravalent chromosomes which ranged fron; O to 14, a.nd 40 chromosomes were counted witout exception in the figures of first anaphase atid second division . 80 chromosomes were obseived- in root tip cells from germinating seeds. Comparisons between diploid and tetraploid plants for tw.o autunn type varieties were tabulated in table 6 about the following characters, namly date of first fiower, time of maturity, total: plant height, number*of node, num, ber of pods per plant, nunl;ber of seeds per plant, fertility (no. of seeds per ovules), diameter of perfect pollen grain, Iength and width of stomatal cell, number of stolnata per unit area, Ieaf index bf 9 th and I O th foliage leaves, mean weight of one seeds, Iength and width of seed, seed shape index and, row protein content. Furthermore it was dscussed ftom the plant bree-ding standpoint about the method of colchicine treat-ment, and the necessity of selection to obtain the constant tetraploid line.