Abstract: Two new crystalline alkaloids were isolated from Senecio cruentus collected from the Shanghai suburb. They are provisionally named cruentine A and B respectively. Cruentine A has a molecular formula C₁₈H₂₅NO₅, m.p. 218-220℃, α_D^17.7 -94.1°. The following salts have been prepared: (1) picrate, m.p. 185-187℃; (2) chloraurate, m.p. 134-136℃; (3) methiodide, m.p. 228-231°. When hydrolysed with 5% alcoholic potash, it gave retronecine and a necic acid C₁₀H₁₆O₅, m.p. 139-141℃. Cruentine B has the composition C₁₈H₂₅NO₆, m.p. 200-202℃, α_D^17.6 -63.4°. Its picrate, m.p. 170-172℃, has been prepared. On hydrolysis as in the case of cruentine A, it also gave retronecine, m.p. 119-120℃, and a different necic acid C₁₀H₁₆O₆, m.p. 177-179℃. The partial structure of cruentine A and B may be expressed as fomula (Ⅰ) and (Ⅱ) respectively. A pale yellowlish volatile oil has also been isolated in a yield of 0.03% which showed some antibacterial action.