It seems best to limit this discussion to the various types of pericarditis, especially as there is little agreement in belief and practice and it is apparent that many cases of this condition, in its different phases, are still overlooked. It is striking that operations for pericarditis are reported from only a relatively small number of clinics. Cooperation between the different services is urgently needed. Much has been accomplished in other clinical fields, such as disturbances of the thyroid gland, diabetes, tuberculosis, peripheral vascular disease, tumor of the lung and many other disease conditions in which the internist and the surgeon are equally interested. The patients with cardiac disease that may come within the scope of surgery should be studied by the internist, roentgenologist and surgeon working in unison. In the clinics from which progress is reported this cooperation is evident. In coronary thrombosis, pericarditis with effusion is sometimes present.