From the tubers of Aconitum karacolicum collected in the Kirghiz SSR (Kungei-Alatau range) we have isolated a new diterpene alkaloid karacoline (I) with the composition C22H35O4N, mp 183-184°C (acetone), mol. wt. 377 (mass spectrometrically). The base contains a N-ethyl group, a tertiary C-methyl group, a methoxy group, and three hydroxy groups. The acetylation of karacoline with acetyl chloride gave a triacetate with mp 165-169°C, and with acetic anhydride in pyridine gave a diacetate with mp 119-122°C, suggesting two secondary and one tertiary hydroxy groups. The mass spectrum of (I) is characteristic for alkaloids with a lycoctonine skeleton; the maximum peak of the ion M-17 shows the presence of a hydroxy group at C1, which is confirmed by the production of an internal β-carbinolamine ether (C22H33O4N, mp 165-195°C (acetone), mol. wt. 375) and the hydrogenation of the product over a platinum catalyst leading to the formation of the initial base. When karacoline was oxidized with chromium trioxide in acetone, a didehydro derivative C22H31O4N was isolated, the IR spectrum of which showed absorption bands of carbenyl groups in five-membered (1740 cm-1) and six-membered (1665 cm-1) rings, limiting the location of one secondary hydroxy group to positions 6, 10, and 12; the presence of a one-proton triplet at 4.16 ppm with a coupling constant of 4.5 Hz in the NMR spectrum of (I) excludes positions 6 and 12 and places the hydroxy group at C10 in the five-membered ring. The benzoylation of the alkaloid with benzoyl chloride in pyridine followed by acetylation formed a dibenzoyl-acetyl derivative with mol. wt. 627, whose NMR spectrum had the acetyl group proton signal at 1.30 ppm (unusually strong field), indicating the hydroxy group at C10 and the tertiary hydroxy group at C8. The methoxy group was located at C15 by the M-91 ion peak (M-59-32) in the mass spectrum of the derivative. On the basis of the above facts, structural formula (I) is proposed for karacoline.