The procedure used with the Du Pont aca for alpha-amylase (1,4,-alpha-D-glucan glucanohydrolase, EC 3.2.1.1) was evaluated in our laboratory and compared with the Roche Diagnostics "Amylochrome" and Perkin-Elmer Coleman 91 amylase assays. The within-run coefficients of variation (CV) for samples of fresh normal sera were: aca 5.8% and 4.3% on two different lots of reagent, Amylochrome 7.4%, and Coleman 91 3.3%. In sera with abnormally high amylase activity, the respective CV's were: aca, 1.2% and 0.8%; Amylochrome, 2.0%; and Coleman 91, 2.8%. Day-to-day precision studies on fresh and lyophilized normal and abnormal sera gave CV's in the following ranges: aca, 1.8% to 6.7%; Amylochrome, 3.0% to 5.2%; and Coleman 91, 4.5% to 5.9%. Results by the aca procedure were linearly related to activity to about 10-fold the upper limit of normal amylase activity. For serum, correlations were: r = 0.977 for aca vs. Coleman 91 and r = 0.974 for aca vs. Amylochrome. For urine they were: r = 0.978 for aca vs. Coleman 91 and r = 0.975 for aca vs. Amylochrome. Mean recovery from 53 supplemented samples was 98%. Icterus, hemolysis, and lipemia did not interfere with method correlation of aca vs. Coleman 91 or Amylochrome.