Five young rabbits were divided into 5 groups (2, 4, 6, 8 and 12 week), one rabbit in each group.A special collision unit was used in the experiment by which the distal ends of the right fore legs of rabbits were struck repeatedly. Altrastructure changes of chondrocyte at the epiphyseal plate in the distal endof radius were observed in H-500 electron microscope. In two and four week groups, organaelles swelling was found such as rough endoplasmic reticulum andmitochondria, especially mitochondria swelling which showed different shapes like sausagge and racket.Space around nucleus increased, nucleus shape changed, myeline structure in the mitochondria and chroma- tin margination in the nucleus were found in the six and eight week groups. Altrastructure changes weremore serious in the eight and twelve week groups than other groups. Necrosis of chondrocyte was appearedsuch as part organaelles dissolved or disappeared, nucleus brokeu aud nucleus memberane disappeared. The results showed in altrastructure pathology that chronic collision injury can cause not only degeneration of chondrocyte in the pressure epiphyseal plate but necrosis of chondrocyte as well. It concluses that chondrocyte necrosis is related to local ischemia resulted from chronic collision injury.