The three-dimensional mean Bow-field and the turbulence quantities k and epsilon have been calculated for a tank stirred with a Rushton turbine. Representing the impeller with the swirling radial jet model and with empirical data gave predictions within the range of reported experimental data. The effect of scale-up using different criteria was investigated. The flow-pattern was mainly inpdependent of scale brit minor changes were found when the Reynolds number was changed.