The senile amyloidoses comprise a heterogeneous group of disorders with deposition of amyloid in a variety of tissues. Most of these amyloidoses are localized to one tissue. It has been shown previously that the amyloid fibrils in one form of senile amyloidosis affecting the heart contains a prealbumin-related protein, ASc1. It is shown in this paper by immunohistochemical study using a specific anti-protein ASc1 antiserum that this type of amyloidosis, previously called senile cardiac amyloidosis, is a systemic disease with amyloid deposits in many organs. The designation senile systemic amyloidosis is proposed for this disease, which differs from other systemic amyloidoses in distribution of amyloid deposits.