Four new norditerpenoid alkaloids, delajacine [7], delajacirine [8], delajadine [9], and ajanine [10], have been isolated from the leaves of Delphinium ajacis along with six known alkaloids. The structures of the new alkaloids 7-10 were determined from the ms and ${}^{1}H$ - and 13C-nmr spectra, including DEPT experiments. The structure of 8 was confirmed by its partial synthesis from anthranoyllycoctonine [3].Previous work on Delphinium ajacis L. (Ranunculaceae) (1-7) demonstrated the presence of twenty-seven lycoctonine-type norditerpenoid alkaloids. In continuation of our efforts to examine the constituents of various parts of the plant, we recently reported the isolation of six known alkaloids from the leaves (6). Of these delcosine [1], delsoline [2], and anthranovilycoctonine [3] had been reported previously from this plant, whereas deltaline [4], delpheline [5], and gigactonine [6] were new to this plant. Wenow report the isolation and identification of four new norditerpenoid alkaloids: delajacine 177, delajacirine 187, delajadine 197, and ajanine {lo], besides six known alkaloids: ajacine 1111, ajadine 1127, delphatine 1137, deltatsine 1141, methyllycaconitine [15}, and 14-acetyldelectine 1167. The known compounds 11-16 have not previously been reported from the leaves. The new compounds 7 and 9 are the first two alkaloids bearing a 2-methylbutyryl group on the -NH side chain of the C-18 anthranilic acid ester. Similarly, compound 8 is the first alkaloid that possesses an isobutyryl group on the -NH side chain. The structure of 8 was confirmed by its partial synthesis from anthranoyllycoctonine 131. Ajanine 110) is the first norditerpenoid alkaloid bearing a 2 hydroxy-2-methylbutyric acid ester group at C-14. The stereochemistry of the new compounds was determined by comparison of chemical shifts of protons and carbons with known compounds of similar stereochemistry.