1. A new alkaloid, pseudocyclobuxin-D, has been isolated from the leaves and fine flowers of Buxus sempervirens. The results of a comparison of the physicochemical properties of pseudocyclobuxin-D and its derivatives with cyclobuxin-D and its derivatives has shown that the alkaloid isolated is an isomer of cyclobuxin-D and has the structure of 14α-methyl-3α,20α-di(methylamino)-4-methylene-9β,19-cyclo-5α-pregnan-16α-ol. © 1975 Plenum Publishing Corporation.