Delphinium brownii Rydb. is a tall larkspur native to the foothills of Alberta. Although preserved at the species level by Ewan [1] in his synopsis of the North American Delphinium, D. brownii is probably better regarded [2] as a local form of D. glaucum S. Wats. The plant is notorious among ranchers as a stock poison. The toxic principles are alkaloidal and previous investigations established the presence of the diterpenoid tertiary bases methyllycaconitine (1) [3, 4] and browniine (2) [4]. We have re-examined the alkaloids of D. brownii and now report that, in addition to 1 and 2, browniine 14-O-acetate (3) occurs in the bases extracted from aerial portions of the plant (both early shoots, and mature flowering stages). Although this acetate has been known [4] as a synthetic derivative of browniine, this isolation demonstrates its natural occurrence [5]. The spectroscopic data which led to our identification of 3 are outlined in the Experimental, and the identity of the alkaloid was clinched by direct comparison with semi-synthetic material. We also found that D. brownii produced small amounts of a quaternary alkaloid, identified as the aporphine magnoflorine. This alkaloid has been reported from some other Delphinium species [6, 7] and we suspect that its distribution within the genus is more extensive than usually recognized, a matter which has to be taken account when attempting to interpret the poisoning produced by the plants.