A new pregnane derivative, 12 beta-hydroxy-5 alpha-pregn-16-ene-3,20-dione, along with the known derivative 12 beta-hydroxy-pregna-4,16-diene-3,20-dione have been isolated from a MeOH extract of the stem of Gelsemium sempervirens and found to be the principal cytotoxic entities. The 13C-nmr spectra of both compounds were assigned by comparison with other pregnane analogs thereby allowing confirmation of the stereochemistry at C-5 in compound. Heteronuclear 2D correlation and selective INEPT experiments indicated the need to revise a number of 13C-nmr assignments of pregn-4,16-dien-3,20-dione. Nine indole alkaloids, gelsemine, gelsevirine, 21-oxogelsemine, gelsedine, 14 beta-hydroxygelsedine, gelsenicine, humantenidine, humantenirine, and koumidine were found to be inactive in the KB and P-388 cytotoxicity test systems.