M USIC LIBRARIES in the United States in the last thirty years have in many cases made progress that enables them to compare favorably with older libraries abroad, especially in their organization, their physical facilities and equipment, and their collections of printed scores and the literature of music. However, in the field of primary source material, particularly autograph manuscripts, of European music, it has long been a common assumption that the American scholar would find our library shelves bare and would have to travel to the great libraries of Berlin, Paris, London, and other European cities to carry on his studies. No one will dispute the pre-eminence of these libraries, of course, in their manuscript collections, but quite aside from the possibility of their treasures being made available in facsimile in this country, it is becoming apparent that a very respectable number of European autograph scores do exist in the United States, in libraries and in private collections. A census of such material, now approaching completion, reveals many treasures of which most musicians may well be unaware. It will be the writer's purpose here to tell something of the background of the census, of some of his experiences in carrying it on, and to call attention to the extent of the manuscript collections in this country. In the spring of 1937 a small group of music librarians, eager to increase available source material in American libraries, outlined a project to obtain microfilm copies of musical rarities in European libraries for a central archive in this country. Approached for a grant to enable a librarian to visit central Europe and make preliminary contacts for such a project, the Oberlaender Trust, although approving the purpose, suggested a preliminary census of autograph manuscripts and facsimiles of European composers in American libraries and collections, and the writer was asked to make such a survey. Once begun, the census proved to be more complicated than expected, and, unfinished at the time of Pearl