Polymorphonuclear leucocyte (PMN) function was determined by measuring whole blood chemiluminescense (CL) in sheep models of amprolium-induced thiamine deficiency. The CL level decreased in sheep with subclinical and clinical thiamine deficiency. The CL level recuperated speedily after treatment with fursulthiamine. These results indicate that PMN function is impaired by thiamine deficiency. (Pathophysiology Section, Department of Production Diseases, TEL +81-298-38-7810)