1. Two new alkaloids have been isolated. One of these, α-pseudaconitine, is isomeric with pseudaconitine. The other is identical with the base obtained on removal of the acetyl group of α-pseudaconitine by partial hydrolysis and it has been named α-veratroylpseudaconine. 2. On complete hydrolysis α-pseudaconitine, like pseudaconitine, gave rise to acetic acid, veratric acid and pseudaconine whereas α-veratroylpseudaconine yielded veratric acid and pseudaconine. 3. Pseudaconine was identified by its analysis, its properties and the preparation of a number of its known derivatives. 4. It was shown that the pyrolysis of tetraacetylpseudaconine produced besides triacetylpyropseudaconine, a small quantity of a hitherto unobserved by-product. 5. The action of 10 N sulfuric acid on pseudaconine gave rise to des-O-methyldemethoxydehydropseudaconine. © 1946, American Chemical Society. All rights reserved.