A colorimetric assay has been developed to quantify alcohol dehydrogenase (ADH) activity. The advantage of this method over conventional spectrophotometric assays is that many samples can be processed at once in a 96-well plate, monitoring the absorbance at 590 nm with a microtiter reader. ADH inhibitors have been used to show the specificity of this method. The assay offers an easy and reliable test for monitoring routine measurements of ADH activity and could be a valuable tool for those involved in the biomedical research of alcoholism, as well as in gene expression methodology in which Drosophila Adh has been widely used as reporter gene in transfection assays.