High-performance liquid chromatography was evaluated as a rapid means of identifying obligately anaerobic gram-positive cocci of medical interest. Isolates were inoculated into a defined chemical medium consisting primarily of amino acids and were incubated aerobically for 1 h at 35 degrees C. After removal of organisms, the supernatant fluids were derivatized for 1 min at room temperature by the addition of o-phthalaldehyde. The total time required to run a chromatogram was approximately 50 min. Standardized peak heights for each medium component and any new peaks formed were calculated for each isolate and compared with those for uninoculated control medium. Multiple isolates of various species of anaerobic gram-positive cocci gave consistent patterns of medium utilization that could be used for identification purposes. This method can easily be adapted for laboratory use and has the potential for automated microbial identification.