A model for dough expansion during oven rise, under conditions where the temperature is independent of position, is presented. The growth of a single gas bubble as a result of the generation of carbon dioxide and water vapour from the surrounding viscous dough is considered. The resulting equations were solved using appropriate numerical methods. The predicted results for oven rise show that the dough volume increases almost linearly with time until a temperature of about 65 degrees C is attained. Above this temperature, the dough expands at a reduced rate and the cell structure starts to set at 85-90 degrees C. The bubble pressure relative to atmospheric pressure is 1.008 in the early stages of expansion, but rises to 1.3-1.4 prior to setting of the dough. The model also indicates that during the initial baking stage the bubble growth is entirely controlled by the partition of carbon dioxide and water vapour between the aqueous and bubble phases. Viscous resistance to bubble growth is important in the later stages of oven rise when the viscosity exceeds similar to 5.0 x 10(5) Pa s. The model shows that it is possible for the eventual termination of oven rise to be caused by the rapidly increasing viscosity which enhances the resistance to bubble growth. Even though elasticity is not taken into account, the predicted dough volumes are found to be in reasonably good agreement with published data for dough baked in a resistance oven, although the bubble pressure at the end of oven rise is higher than predicted. It is suggested that in some cases the cell rupture resulting in the open cell structure for bread could be a consequence of the increased pressure and not the cause for the termination of oven rise.