To characterize the physical demands associated with on-the-job use of current firefighting equipment and the performance of essential firefighting operations, an initial task analysis of all firefighting operations was followed by an in-depth physical and physiological characterization of those tasks deemed to be physically demanding. The most commonly encountered applications of strength and endurance were lifting and carrying objects (up to 80 lbs), pulling objects (up to 135 lbs), and working with objects in front of the body (up to 125 lbs). The most demanding firefighting operations required a mean VO2 of 41.5 ml/kg.min-1 with peak lactate concentrations of 6 to 13.2 mM. Ninety percent of the demanding firefighting operations that were studied required a mean VO2 of 23 ml/kg.min-1. These aerobic energy requirements corresponded to 85 and 50% VO2max, respectively. Therefore a minimum VO2max standard for firefighter applicants of 45 ml/kg.min-1 is recommended.