The polyamine fractions extracted from soybean and natto (a fermented soybean food) were analyzed by high-performance liquid chromatography and gas chromatography. Putrescine, spermidine and spermine, as the majorcomponents, and cadaverine, homospermidine and agmatine, as a minor polyamine, were similarly detected in the whole polyamine extracts from both soybean and natto. An analysis of the polyamine extract from the glutinous surface substance of natto showed a high concentration of agmatine, this concentration increasing during the fermentation progress of natto. Agmatine was also produced in the pure cultured Bacillus natto used for natto fermentation.