This report gives the results of an evaluation of a Hewlett-Packard Model 5993B computerized gas chromatograph/mass spectrometer. The evaluation was done according to the procedures found in EPA research report number EPA-600/4-80-025, 'Performance Tests for the Evaluation of Computerized Gas Chromatography/Mass Spectrometry Equipment and Laboratories.' Changes in the 'Performance Test' specifications for the BFB spectrum validation test have been made and are noted in the results for Tests 1 and 8. The system performed satisfactorily during the evaluation and is acceptable for the analyses of organic compound using methods similar to EPA Methods 624 and 625. The HP-5993B system produced valid mass spectra, exhibited good to excellent stability, and gave a satisfactory detection limit. The precision and accuracy for external or internal quantitation using direct sample injection or purge and trap were excellent. Both 14 AMU and PBS mass spectral library searches were accurate; however, the search times using the PBS library search were longer than the requirements 'Performance Tests'. Some problems, particularly with brominated compounds, were discovered during this evaluation. The manufacturer corrected the instrument to alleviate these problems.