A detailed study of the output energy characteristics of the pulsed, optically pumped 4.3‐&mgr;m CO2laser is described. The predictions of a rate‐equation model representing the laser dynamics are shown to be in good agreement with experiment over a wide range of operating conditions. The factors which control the performance of the laser are identified, and the optimum operating conditions for maximum output energy are discussed. Output energies of 15 mJ/pulse and peak powers of 100 kW/pulse have been obtained from an 88‐cm‐long by 11‐cm2‐aperture discharge. Scalability of the pulse energy to several hundred mJ using available pump pulse energies is shown to be feasible.