In order to analyse stress distribution at the human mandible during biting, three dimensiona1finite element codes SAP6 and NISA II were employed. Two kinds of finite element models of mandibles symmetrical and nonsymmetrical shapes and load conditions determined by X-ray CT measurements were adopted to calculate the stress distribution. The computational results showed that the stress distributes in the entire area of these mandibles, but the stress around the condyle is less than the other regions. At the same time, Ca density distribution of the mandibles was measured by the same X-ray CT. These results showed strong relationship between stress and Ca density distributions.