To investigate expression of pancreas serine elastase mRNA in the tissues and organs of normal rats. Methods Rat pancreas serine elastase Ⅱ RNA probe was cloned and labeled with digoxin. The tissues and organs of normal male Wistar rats were taken and fixed in 4% paraformaldehyde. In situ hybridization was then performed. Results Expression of elastase mRNA has been found in the endothelial cells, the medial smooth muscle cells and the adventitial fibroblasts of the abdominal aorta, the lymphocytes, monocytes in blood, the tracheal hyaline cartilaginous cells, the glandular cells of the pancreas, the epithelial cells of the parotid gland and submaxillary gland, the hepatocytes, the endothelial cells of the liver sinusoid wall, the goblet cells of the mucous membrane of the small intestine, the cardiac myocytes, the renal interstitial fibroblasts, the alveolar epithelial cells, the cerebral glial cells, the fibroblasts of the dermis corium of the skin, the primary spermaocytes, the secondary spermaocytes and sperm in the seminiferous tubule of the testis, the lymphocytes in the spleen and thymus. Conclusion Elastase mRNA expressed extensively in the tissues and organs of rats described above.