An amyloclastic method of amylase measurement using iodine merely as a differential stain is described. The technique is applicable to high amylase activities (25-750 IU/ml) as encountered in saliva or in purification procedures. Normal serum amylase levels are below the threshold of this method. Thin starch-agar plates of constant composition are poured on a transparent base, small wells are filled with constant microvolumes of samples, and two concentrations (e.g., 50 and 500 IU/ml) of α-amylase standard are included with each plate. After a constant time (e.g., 2 hr) of incubation at 37°C, the plates are developed and immediately thereafter diameters of amylolytic zones are recorded to tenths of millimeters. Unknown concentrations are derived by geometric or arithmetic comparison with the reference standards on the same plate-keeping in mind the linear relation between diameters and log concentrations. Concentrations from replicate plates are averaged. The estimated coefficient of variation is 11.5%. Greater accuracy can be obtained by using the average of replicate plates. © 1969.