Adherent pericarditis is acknowledged to be one of the most difficult cardiac conditions to diagnose, and this statement is confirmed by analysis of records of necropsies. In relatively few cases is the condition positively identified while the patient is alive. Numerous reasons exist for this inaccuracy of diagnosis. Foremost among them is the clinician's lack of suspicion regarding the possible existence of the disease. There may be complete absence of symptoms and signs, and this obviously renders identification of the disease impossible. The didactic overemphasis on so-called characteristic signs has gone far toward frustrating correct diagnosis, for in reality such signs exist in relatively few cases, and their absence often influences the clinician against committing himself. The occurrence of associated disease entirely unrelated to the cardiovascular system may so dominate the clinical picture that attention may be exclusively centered on the principal disease. Likewise, associated disease of the heart may