If the broad definition of inflammation proposed by Marchand, with the adherence of many other pathologists, is accepted, it may be said that except for congenital anomalies, retrogressive changes such as amyloid, and tumors, the lesions of the human endocardium all have certain features that may be regarded at least in part as inflammatory. ENDOCARDIAL SCLEROSIS Valve leaflets, especially aortic and to a lesser degree mitral, as well as the mural endocardium, particularly that of the septum near the aortic orifice, frequently exhibit fibrous thickening, atheroma and calcification which justify the conclusion that the lesion is essentially the same as intimal arteriosclerosis. Indeed, the association of such endocardial sclerosis with sclerosis of the aorta is almost constant. In the aortic leaflets the fibrosis is especially prominent at the attached bases of the valves and is still most conspicuous in this situation after the entire leaflet becomes notably thickened and stiff.