Geissovelline, C23H30N2O4, is a new dihydroindole alkaloid from the bark extract of Brazilian Geissospermum vellosii. Based on the chemistry of the unusual functional groups, e.g., a tertiary nitrogen which interacts transannularly with an α,β-unsaturated ketone carbonyl, structure 3 is proposed for geissovelline and is supported by complete analyses of proton and carbon-13 nmr spectra of deacetylgeissovelline (28). The reactions of this alkaloid are unparalleled. Deacetylgeissovelline is readily pyrolyzed to 1-ethyl-6,7-dimethoxycarbazole. Lead tetraacetate oxidation of deacetylgeissovelline prior to pyrolysis, on the other hand, leads to compound 6. A detailed procedure for the separation of the alkaloid-rich bark extract of Brazilian Geissospermum vellosii into various fractions using liquid-liquid extraction at different pH's has been described. Further purification of the weakly basic fraction B or fraction 13 by chromatography on alumina has resulted in the isolation of a new crystalline alkaloid, geissovelline, and the structure determination and chemistry of this new alkaloid is the subject of the present report.