Amyloidosis refers to disorders that cause organ failure due to amyloid deposition. Deposited amyloid is clearly stained by Congo red and is detected by apple-green birefringence under polarized light. Amyloid fibril proteins are very stable, but several recent studies have revealed that amyloid deposition and the clearance of fibrils cause the steady turnover of deposited amyloid proteins. Therefore, in several amyloidosis disorders, especially primary AL, reactive AA, and transthyretin-related amyloidosis, effective therapies are expected to cause the regression of tissue-deposited amyloid.