The crack growth process in rolling contact fatigue has been investigated on ring type plate specimens, in which and crack growth is observed on the side surface of the specimens. The results have shown that cracks in high carbon chromium bearing steel are initated from contact surface to the direction approximately normal to the contact surface. After some short length of growth. crack grows parallel to the contact surface and it grows until the separation of the surface layer, inducing flaking type failure. Silicon nitride shows a contact fatigue behaviour similar to that typically found in metallic material. From the fractographic and metallographic observations, it has been found that the crack initation in the silicon nitride subjected to rolling contact fatigue is to be induced by cyclic subsurface shear stress, as is known in high carbon chromium bearing steel.