Engineering design data for agitator vessels as fermentors. The article develops and collects design data for stirring vessels for calculation of mass and heat transfer and the flooding point and stirrer power requirements for aerated liquids. The data refer to low-viscosity, higher viscosity, and structure viscosity liquids with difering coalescence behaviour. The working data presented are used to derive results for a specific system (air/aqueous solution of carboxymethylcellulose) which illustrate decisive relationships and limitations arising from mass and heat transfer. There results important information for the operation, and choice, and scale-up of stirred fermentors.