As one interested in radiology, you are cordially invited to come to Baltimore, Maryland, Monday, Tuesday, and Wednesday, September 15, 16, and 17, 1930, for a post-graduate teaching course, with lantern slides, on the diagnosis and treatment of diseases and tumors of bone. You may extend this invitation to any member of the medical profession who is interested in the problem as a radiologist, pathologist, internist, or surgeon. We are anxious that this invitation shall reach those members of the medical profession who see least of bone lesions and want help most in the diagnosis and methods of treatment. The demonstrations will be held in the ballroom of the Belvedere Hotel, Charles and Chase Streets, Baltimore, Maryland. On account of the size of the ballroom the number is limited to eight hundred. If you desire to attend this demonstration, which begins Monday morning, September 15, at 10 o'clock,1 write at once to the Manager of the Belvedere Hotel to reserve accommodations, and by so doing automatically register for the demonstration. It is requested that you specifically state whether you will be there Monday, Tuesday, or Wednesday, or all three days. The Manager of the Belvedere Hotel will be willing to give reduced rates to those who desire them. When writing, therefore, ask for the usual rates for single and double rooms, with and without bath; for special rates of three or more in a room, with and without bath, and for the special restaurant rates of club breakfast, luncheon, and dinner. It is very important for you to keep the final letter from the Belvedere Hotel and present it when you register. The demonstrations will take place from ten to twelve-thirty in the morning, two to four-thirty in the afternoon, and seven to nine-thirty in the evening. The demonstration Monday will be devoted to the simplest fundamentals of the clinical picture, X-ray and gross and microscopic pathology of osteitis fibrosa, giant-cell tumor, osteomyelitis, exostosis, benign bone tumors, sarcoma, multiple myeloma, and metastatic tumors. Four lanterns and screens will be employed in the demonstration. Tuesday will be devoted to the differential diagnosis of lesions of special bones—lower end of radius, upper end of humerus, vertebrae, etc. Wednesday will be reserved for the presentation of rare and very difficult-to-diagnose lesions of bone. Anyone planning to attend this meeting may at once register such a case or cases observed personally or by some colleague, addressing Miss Maude Walker, Secretary to Dr. Bloodgood, Surgical Pathological Laboratory, Johns Hopkins Hospital, Baltimore, Maryland. Accompanying this registration must be the X-ray films, or lantern slides, a brief clinical history, and, if an operation has been performed, sections of tissue. If you cannot send lantern slides, we will make them ourselves from the X-ray films and microscopic sections.