Aliquots of whole blood from two separate Vacutainer tubes are diluted with 1-propanol as an internal standard before analysis by headspace gas chromatography (HS-GC) with three different stationary phases; Carbopak B, Carbopak C, and 15 percent Carbowax 20M. Computer-aided techniques are used for the actual HS-GC analysis, the integration of chromatographic peaks, the collection and processing of results, and the quality control tests. The standard deviation of analysis (y) increased with concentration of ethanol in the blood specimen (x). The prosecution blood-alcohol concentration (BAC) is the mean of three separate determinations, each made by different laboratory technicians working independently with different sets of equipment. To compensate for random and systematic errors inherent in the method, a deduction from the mean analytical result is made. 6 figures, 3 tables, 16 references. (Author abstract modified)