Isolation of solanidine(1), etioline(3) and verazine(2) as main alkaloids from the terrestrial part of budding Veratrum grandiflorum (Max.) Loesen, has been reported. In addition to veratramine, two new alkaloids, teinemine((22R, 25S)-22, 26-epimino-cholesta-5-ene-3β, 16α-diol)(6) and isoteinemine((22S, 25S)-22, 26-epiminocholesta-5-ene-3β, 16α-diol)(7) were identified from the secondary alkaloid fraction in HCl hydrolysate of budding leaf glycoside. From the accumulation of three 22, 26-epiminocholestenes (etioline(3), verazine(2) and teinemine(6)) in the budding veratrum, they seemed to have an important role in the biosynthesis of solanidine(1). And the hypothetical pathway of solanidine(1) biosynthesis with these 22, 26-epiminocholestenes could be proposed. The next problem in our studies of solanidine(1) biosynthesis was to determine its nitrogen origin. In the cautious detection of annual change of alkaloids in veratrum plant, we found that verazine(2) already accumulated in the dormant rhizome, then we detected quantitative change of free amino acids and ammonia in whole plant during dormant period. Only L-arginine showed the significant change was appeared at just before the accumulation of verazine(2) in the rhizome. This result suggested that L-arginine was the possible nitrogen origin in solanidine(1) biosynthesis. And this suggestion was strongly supported by that the feeding experiment of ^<15>N-L-arginine with [4-^<14>C]-cholesterol showed the higher existence and incorporation of ^<15>N in solanidine(1) than ^<15>N-NH_4Cl feeding.