This study investigated the alkaloid constituents of the root bark of Alstonia scholaris R.Br. (Apocynaceae), sourced from the Botanical Garden of the Department of Medical Sciences, Thailand (voucher sample ALST 101-731). Previous work had isolated echitamine and echitamidine from the plant. Alkaloids were extracted with 2% ammoniated methanol and fractionated into weak, intermediate, and strong base fractions using chloroform at pH 1, 8, and 11. Six previously unreported alkaloids were detected: five were isolated and identified (including +akuammigine, tubotaiwine, akuammicine, akuammicine-N,,-oxide, akuammicine-Ns-methiodide, and N,-demethylechitamine) via spectral methods (UV, IR, MS, NMR) and comparison with authentic standards or synthetic derivatives, while one was identified by co-thin-layer chromatography (co-TLC). The major alkaloid in the strong base fraction was echitamine (isolated as its chloride, accounting for 0.21% of the root bark). Other alkaloids quantified included N,-demethylechitamine (0.002%) and +akuammigine (0.0004%).