Acotoxinine (1), a new norditerpene alkaloid, was isolated from the roots of Aconitum toxicum RCHB., together with the structurally related C19 diterpene alkaloids neoline (2) and aconitine (3) and C20 diterpene alkaloids songorine (4) and songoramine (5). The structures were elucidated by HR-MS and advanced NMR methods, including 1H-NMR, JMOD, 1H,1H-COSY, HSQC, and HMBC experiments. This is the first report of C20 diterpenoid alkaloids in Aconitum toxicum. © 2006 Verlag Helvetica Chimica Acta AG.