We describe an improved method for detecting deficiency of the acid hydrolase, 
alpha-1,4-glucosidase in leukocytes, the enzyme defect in glycogen storage 
disease Type II (Pompe disease). The procedure requires smaller volumes of blood 
and less time than previous methods. The assay involves the separation of 
leukocytes by Peter's method for beta-glucosidase and a modification of Salafsky 
and Nadler's fluorometric method for alpha-glucosidase.