Arthroscopic, macroscopic and histological signs of degenerative changes in the articular disc were found in 228 temporo-mandibular joints from corpses. In this way it was possible to identify a degenerative development series. Three preferred sites are typical of degenerative metaplastic processes: antero-lateral in the fibrocartilaginous section, lateral at the transition between fibrocartilaginous and bilaminar section and postero-central in the bilaminar zone. The beginning of a degenerative process was never detected in other sections of the disc. Degeneration commences in the fibrocartilaginous section with fragmentation of the collagen fibres, destruction of interzellular substance and loss of collagen fibres proceeding from the cranial surface. This leads to thinning, rupture and, finally, to dehiscence. In the bilaminar zone the degeneration develops in the caudal section of the cranial lamella. It leads to ganglia formation due to mucoid liquefaction. After tearing of the cranial lamella the caudal lamella thins down until it finally ruptures. Dehiscence thus occurs dorsally, too.