Our results indicate that most of the saponins in mungbean (Vigna radiata) cannot be identified at present because of lack of adequate analytical procedures. While TLC is adequate for monitoring the saponins in the analytical scheme, it does not provide the information obtained by HPLC, which can be used to obtain pure saponin fractions from the plant material. Use of liquid secondary ion mass spectrometry to determine the partial structure is outlined and discussed on pure soyasaponin-I, alfalfa seed saponins which serve as the biological control, and crude saponin samples from mungbeans; it showed that these were about 40% soyasaponin-I, with most of the remaining saponins being unknown. The local cultivar, Chai Ly, contained the most unknowns, which was interpreted to mean that the breeding of the more recent cultivars such as Tainan No.3 and No.5 has caused the loss of the ability to make some of the unknown saponins. A completely unexpected finding was that the addition of saponins to soil enhances the growth and development of the mungbean plant, but not the yield. A mechanism of action of the saponins and hydrolyzed saponins is proposed. [AS]