Fermentation of cholic acid with Arthrobacter simplex (IICB 227) under aerobic conditions yielded 3,12-dioxo-23,24-dinorchola-4,6-dienoic acid, 7 alpha-hydroxy-3,12-dioxo-23,24-dinorchol-4-enoic acid, 3 alpha, 7 alpha-dihydroxy-12-oxo-5 beta-cholan-24-oic acid, 3 alpha, 7 alpha-dihydroxy-12-oxo-5 beta-23,24-dinorcholan-22-oic acid, 7 alpha, 12 alpha-dihydroxy-3-oxo-5 beta-cholan-24-oic acid, 7 alpha-12 alpha-dihydroxy-3-oxo-4-cholenoic acid, 7 alpha, 12 alpha-dihydroxy-3-oxo-23,24-dinorchol-4-enoic acid, and methyl-3 alpha-7 alpha, 12 alpha-trihydroxy-5 beta-cholan-24-oate in addition to a new metabolite 2 beta-hydroxy-3,12-dioxo-23,24-dinorchola-4,6-dienoic acid. Each microbial metabolite was characterized by the application of various spectroscopic methods. The availability of some of the metabolites' enabled complete elucidation of their 13C NMR spectra.