AMONG NEARLY 3,200 autopsies performed at St. Vincent's Hospital over a period of fifteen years, 5 cases of amyloidosis were discovered, 1 of which is believed to be a clearcut example of the primary atypical form. The purpose of this paper is to attempt to justify the use of the term "primary atypical" as accurately descriptive of this type of amyloid disease. Three factors have made satisfactory classification of amyloidosis difficult. The first is the confusing variety of terms employed by authors in describing their cases; the second is the wide variation in anatomic distribution of the amyloid revealed at autopsy; the third, and probably most fundamental, is the fact that little is known of the immediate cause, or causes, of the deposition of amyloid in the tissues. To date, approximately 70 cases belonging in the category of primary amyloidosis have been reported in the literature. Terminology used by the