The Alco Screen Saliva Dipstick is an inexpensive, easy-to-use, colorimetric test that gives a semiquantitative estimation of the blood alcohol value by measuring the relative concentration of salivary alcohol. To evaluate its accuracy, we compared the results from tests with the Alco dipstick with values from simultaneously measured blood alcohol tests in 53 patients who were suspected of having ingested alcohol. The correlation between Alco dipstick results and blood alcohol values was strong (r [Spearman's rho], + .91). When the blood alcohol concentration was 0.1 g/dL or more, the Alco dipstick test was 90.9% sensitive, 71.4% specific, and 92% efficient. At Alco dipstick values of 0.02 and 0.05 g/dL, however, semiquantitative concordance was unsatisfactory. Nevertheless, even at the 0.05-g/dL value of salivary alcohol, the test was still valuable as a screen of de facto alcohol ingestion. Definitive diagnosis of relative alcohol intoxication requires confirmatory breath or blood alcohol concentrations by standard methodologies.