The fate of the articular cartilage of the hip joint with intracapsular neck fracture was studied by histological, histochemical and autoradiographic techniques and by using a polarized microscope and a scanning electron microscope. Cartilage specimens from 93 femoral heads and 7 acetabula were obtained from fractured hips 2 days to 4 1/3 years postfracture and from control hips with various disorders. The cartilage degeneration appeared 2 weeks after fracture and advanced steadily with time. The matrix was covered, invaded and ultimately replaced by the fibrous tissue. Chondrocyte viability, though it was lost from the surface, was recognized in the deep matrix even in the oldest fracture examined. It is concluded that the humoral factor directly caused by the injury as well as the biomechanical impairment, i.e. a loss of physical stress, may play an essential role in the pathogenesis of the degeneration. The possibility of regeneration was discussed.