Amyloidosis is characterized by deposition of amyloid, which is resistant to proteolysis & phagocytosis, in intercellular spaces & vascular walls. The amyloid deposition provokes dysfunction of an accumulated organ & displays variable clinical symptoms depending upon the involved organ. A diagnosis is rendered through a biopsy of the affected organ, followed by staining using congo red which reveals an apple greenish refractile birefringence via polarizing microscopy. Using an electro-microscopy specific filaments can be found. Amyloidosis is classified into primary amyloidosis, composed of light chain filaments (AL) and secondary amyloidosis, comprised of A protain (AA). The AL type of amyloidosis shows deposition of amyloid in muscularis mucosa & muscularis externa. Priunary amyloidosis on the other hand, is relatively rare. We experienced primary stornach amyloidosis (AL), which was mistaken for stomch cancer. (Korean J Gastrointest Endosc 18: 561-566, 1998)