The Technicon AutoAnalyzer II was evaluated for automatic quantitation of non-casein protein (NCP) in milk. The Lowry method f or colorimetric measurement of proteins was adapted to the automated method and found to be accurate in the determination of non-casein protein in milk. The automated Lowry method obeyed Beer's law. Casein content was calculated by difference between total protein determined by infrared milk analysis (IRMA) and non-casein protein. In the analysis of twenty-five replicate milk samples, the standard deviation was 0.32 and the coefficient of variability was 0.90. The casein content as a percentage of total protein in the milk of cows in the Utah State University dairy herd was found to vary from 41.0 to 81.3%. The automated or continuous flow method was affected by as little as 0.05% (w/w) mercuric chloride, a chemical preservative used in milk, whereas potassium dichromate and formaldehyde had insignificant effects upon the assay.