Theoretical analysis of flame propagation through catalytically activated mixtures and fundamental experiments with a catalytic plug-flow reactor have shown that catalytic prereaction can increase flame velocity and can reduce minimum ignition energy requirements. These principles have been successfully applied in a prechamber for a leanburn internal combustion engine. Unlike other catalytic engine concepts, catalytic prechamber technology serves to regulate catalytic surface temperature as well as contact between the catalyst and gas phase reactants. Catalytic effects are thus properly timed and are confined to a small volume where substantial thermal activation is possible. Catalytic charge activation in a CFR engine was found to decrease cycle-to-cycle pressure variation and to increase cycle efficiency near the lean-burn limit. These effects were found to be more pronounced as the prechamber was made more adiabatic. When catalytic prereaction was more extensive the catalytic prechamber proved to be a knock-free compression-ignition source. In conjunction with these fundamental studies and parametric engine tests a physical model of in-cylinder activation has been formulated. This model has proven to be a valuable asset in understanding catalytic prechamber performance and promises to be a useful tool in optimizing catalytic prechamber design.