Characteristic patterns of the pressure curves from the right auricle and the right ventricle have been found in chronic constrictive pericarditis by various investigators. It has been uncertain, however, whether or not the findings were pathognomonic, and whether they were reliable pictures of the pressure conditions or artefacts. Consequently the views upon the underlying mechanism have been different too. It is concluded from the studies here presented that the pressure curves are pathognomonic when in their most pronounced form, and that they are not artefacts and thus furnish a proper basis for inferences as to the hemodynamics in chronic constrictive pericarditis.