The correlation between disc displacements in the temporomandibular joint and the petrotympanic, petrosquamous and tympanosquamous fissures was investigated in 38 corpses. Only 12 joints had no ossification of the fissures, while 26 joints were partially ossified. With one exception, none of the joints with non-ossified fissures revealed disc displacement. In contrast, all the joints with ossified fissures revealed disc displacement. Women proved to have more displaced discs than men. On the basis of the findings, a model of the etiology of disc displacement is discussed.