When a patient presents himself with the common complaint of pain in the shoulder region and arm, with or without limitation of motion and unrelated to severe trauma, the physician usually thinks of the joints, bursae, tendons or nerves rather than of the shoulder girdle muscles as the primary source of pain. Thus the customary diagnosis in this type of patient is either arthritis, subacromial bursitis, brachial neuritis or radiculitis. The well known chronicity of these symptoms and the variety of therapeutic procedures employed suggest either that the customary methods of treatment are unsatisfactory or that the underlying cause is often overlooked. It is our purpose in this report to discuss the diagnosis of a type of pain in the shoulder and arm which has its origin in the muscles of the back or shoulder girdle and to present the results of an effective method of therapy, namely intramuscular infiltration