A reliable method is presented for rapidly screening human sera to detect macroamylasemia. A mixture of the serum to be tested, Blue Dextran, and cytochrome c is filtered through a small column of cross-linked dextran gel (Sephadex G-100). Amylase in the effluent fractions is detected by incubation with amylose and subsequent addition of iodine. Macroamylase, if present, is found in the blue-colored fractions, while amylase of normal molecular weight appears in the fractions colored by cytochrome c.