Abstract: Gentianidine(C₉H₉O₂N) is a new alkaloid isolated from the Chinese drug "Chin-Chiu" —Gentiania macrophylla. It is a lactonic tertiary base and is optically inactive. The infrared spectrum of gentianidine showed the presence of an a,β-unsaturated δ-lactone and C-methyl group(s). Oxidation of gentianidine with potasium permaganate in 1N sodium hydroxide produced berberonic acid (Ⅱ), identical with an authenic sample obtained from the oxidation of berberine. According to these results, two possible structures for gentianidine, Ⅲ and Ⅳ, can be advanced. Comparison of NMR spectra of gentianidine and gentianine precluded structure Ⅳ, leaving Ⅲ as the favoured alternative. Proof of structure for gentianidine by synthesis was accomplished by treatment of the condensation product from 4,6-dimethylnicotinic acid and formaldehyde with 2N HCl at 100°for 17 hours.