14-Hydroxycodeine and norcodeine were rigorously identified as products arising from codeine oxidation by Streptomyces griseus ATCC 10137. Both products were routinely detected in extracted culture filtrates after growth of cells in the presence of codeine for 1 week. Under these conditions, about 4 mol% of the codeine starting material was consumed, with norcodeine and 14-hydroxycodeine representing the only identifiable transformation products (molar ratio, 4:1, respectively). Extraction of a series of culture filtrates and purification of the pooled metabolites by thin-layer and high-pressure liquid chromatography led to the isolation of both biological products, the structures of which were verified by high-resolution mass spectrometry and proton nuclear magnetic resonance spectroscopy. The identities of both biological products were further confirmed by comparison of their spectral properties with those of authentic standards. This is the first report providing structural evidence for the biological formation of 14-hydroxycodeine from codeine and of codeine oxidation by S. griseus.