Enzyme catalyzed introduction of the 1-2 double bond into a steroid can be monitored through spectrophotometric changes accompanying electron acceptor reduction or through paper or thin-layer chromatographic analysis of the reaction product. The spectrophotometric method is not applicable to cases in which the oxidized form of the electron acceptor is continually regenerated. In studying such cases, we have found high pressure liquid chromatography (HPLC) to be a method of direct analysis more convenient than paper chromatography or tlc. Use of a water based eluant and a reverse phase column for the HPLC analysis allows direct injection of a sample of the aqueous reaction solution after acidification, and no extraction with an organic solvent is necessary. © 1975.