An evaluation of the EMIT-st serum alcohol assay is reported. Although the assay was developed as a qualitative procedure, the day-to-day precision of the test with respect to the differences in absorbance (delta A) was evaluated, in order to establish its applicability for quantitative analyses. The mean values +/- SD (n = 10) for the delta A of the positive control and the cutoff calibrator were 146 +/- 14 (CV = 9.6%) and 57 +/- 5 (CV = 8.8%) respectively. The detection limit of the assay was 0.3 mg/ml ethanol. A series of spiked serum samples with ethanol concentrations in the range of 0.1 to 4.0 mg/ml was analyzed in triplicate by EMIT-st and by gas chromatography. Qualitatively, the correlation between these two methods was nearly 100 percent. For the EMIT-st assay, the response was only linear between 0.3 and 2.0 mg/ml ethanol. Concentrations higher than 2.0 mg/ml showed no pronounced difference in absorbance measurements. Serum samples (n = 54) of people involved in automobile driver alcohol blood checks were analyzed by EMIT-st and the results were compared to the corresponding gas chromatographic data. In the range up to 2.0 mg/ml ethanol, a linear regression curve was calculated with a slope of 76.7, a y-intercept of 36.4, and a correlation coefficient of 0.79. Spiked serum samples at concentrations of the calibrator and the positive control as provided by Syva appeared to be identical in delta A response.(ABSTRACT TRUNCATED AT 250 WORDS)