Failure analyses were conducted on the top piston rings from selected Caterpillar 1K tests. Metallography, scanning electron microscopy, and X-ray spectroscopy were applied to characterize the top ring surface and subsurface damage.Pitting an erosion of the ring's hard facing characterized the damage observed in the scuffing cases studied. These observations support the theory that top ring failure may have started the chain of events that lead up to piston scuffing in the 1K.The top ring damage may be the result of corrosive combustion by-products that are formed in the ring belt area. The analyses in all three cases indicated that top ring failure had occurred prior to piston skirt scuffing. Several hypotheses are offered as to what may have initiated this top ring failure.