Firefighters work at maximal levels of exertion. Fitness for such duty requires adequate aerobic capacity (maximum oxygen consumption [Vo2max]). Aerobic fitness can both improve a worker's ability to perform and offer resistance to cardiopulmonary conditions. Inactive firefighters have a 90% greater risk of myocardial infarction than those who are aerobically fit. Participants (101 firefighters) completed a questionnaire that asked them to rank their fitness level from 0 to 7; e.g., Level 0 was low fitness: "I avoid walking or exertion, e.g., always use elevator, drive whenever possible." The level of activity rating increased to Level 7: "I run over 10 miles per week or spend 3 hours per week in comparable physical activity." Each participant then completed two measures of Vo2max: a 5-minute step test and a submaximal treadmill test. There was no association between the firefighters' self-perception of their level of fitness and their aerobic capacity as measured by either step test or submaximal treadmill. Because of the critical job demands of firefighting and the negative consequences of inadequate fitness and aerobic capacity, periodic aerobic capacity testing with individualized exercise prescriptions and work--community support may be advisable for all active-duty firefighters.