A simple, rapid method for the determination of P-type isoamylase with the use of a commercially available a-amylase inhibitor is presented in detail. The procedure described herein has been developed for use with the Beckman DS amylase kit and BMD amylase-UV kit and has been adapted to the COBAS-Bio and the Hitachi 705 analyzers. The method can readily be modified for use with other manual or automated methods and is suitable for routine as well as emergency use.