Continuing a study of the alkaloids of the seeds of Haplophyllum perforatum collected in the "Galliya-Aral" collective farm, we isolated from the neutral fraction of a petroleum ether extract, in addition to eudesmine and haplamine, a new base (I) with mp 143-144°C (ethanol), [α]~-35.12° (c 2.189; methanol). The content of haplamine was 0.15% and that of substance (I) 0.005% on the weight of the seeds. Haplamine remained in the neutral fraction with eudesmine as it was not extracted by 10% acid from an ethereal solution. The base (I), C₁₈H₂₃NO₄, M⁺ 317, was obtained from the first ether eluates when the neutral mother liquor was chromatographed on alumina. It dissolves readily in ether, benzene, and chloroform, is insoluble in dilute acid and alkali, and has an Rf of 0.88 in the toluene-ethyl acetate-formic acid (5:4:1) system in TLC (silica gel). A direct comparison with an authentic sample showed (I) was identical to anhydroperforine. In the NMR spectrum of anhydroperforine (taken in benzene on a JNM-4H 100/100 MHz instrument), a narrow quartet at 5.94 ppm with J₁=2 Hz, J₂=3.5 Hz from the proton at C7 indicates the equatorial nature of this proton and thus the cis linkage of rings A/D, with the methoxy group at C8 in an axial position. Anhydroperforine is the third representative of the 5,6,7,8-tetrahydrodictamnine series. To date, alkaloids of this group have been found only in the seeds of H. perforatum.