Ten bovine omasa showing more or less deformed laminae omasi are described and classified into two groups: one group (I) without and one (II) with macroscopically perceptible inflammation. The possibility that groups II and I are two successive stages of the same process in which necrotizing inflammation plays an important role, is pointed out. The malformation of the bovine omasum described in the literature as aplasia or hypoplasia, bears a resemblance to the malformation in group I, and, in this case, necrotizing inflammation also was the probable cause.