The Cam-Clay model for isothermal mechanical behaviour of clays has been extended to take account of the effects of temperature on stress-strain behaviour. The assumptions used in constructing the new model are based on published results and on new data presented in the paper. The model allows prediction of how heating and cooling affect volume changes, pore-water pressures, and strengths for both normally consolidated and overconsolidated saturated clays. It permits modelling of observed reductions in the overconsolidation ratio with increasing temperature. The model provides accessible qualitative explanations for temperature effects that were previously difficult to understand. It will also allow easy implementation for quantitative modelling in triaxial stress fields. Results predicted by the model are compared with data collected by the authors at temperatures up to 100 degreesC. The model does not account for changes that occur in clay minerals at higher temperatures, for example, in bentonites at temperatures higher than about 150 degreesC.