Healthy male and female subjects in the 18 to 55-year range were given alcoholic drinks of their choosing. The doses were varied to obtain a wide range of blood alcohol levels. Simultaneous breath and blood samples were taken 1 hour after the last drink when the majority of subjects were in the alcohol elimination phase. The results of in vitro measurement of the Alcolmeter's precision, using aqueous alcohol synebriate standards equivalent to five BAC's in the range 0-25 mg percent, compared well with other evaluative studies that reported high accuracy. In vivo analyses of 22 blood and breath samples resulted in a standard deviation of 10.6 mg. percent under the most favorable laboratory conditions and with healthy subjects. This compares favorably with another study using a much greater number of instruments under field conditions. Comparative analyses of headspace blood and of headspace saliva using the Alcolmeter AE-D1 and the conventional gas chromatography on 51 samples resulted in standard deviations of 7.6 mg percent and 7.2 mg. percent, respectively. In conclusion,the Alcolmeter fuel cell detector instruments have probably achieved the greatest possible degree of accuracy in determining BAC levels by breath analysis. Also, the simplicity of the instrument, coupled with its high sensitivity, lends it to field use. In addition, it has the added feature of a highly simplified method for blood and saliva analysis requiring no sample dilution. Five figures and 14 references are provided.