This study was conducted to examine the age and sex related differences in upper body muscular endurance among active duty firefighters (FF). Methods: Muscular endurance was assessed using the standard YMCA Bench Press protocol on 535 (502 male and 33 female) active duty FF. Subjects were categorized by age ( < 35 years of age or > 35 years of age) and sex (male or female). Males FF lifted a 80 pound bar and female FF lifted a 35 pound bar through the full range of motion, at a set cadence, with proper form until subjects reached fatigue. Raw scores as well as age and gender percentile rankings were then analyzed to determine if differences exist. Level of significance was set at p < 0.05. Results: Significant mean raw score differences existed between young (37.6 reps) and old (32.3 reps) male FF but not between young (50.8 reps) and old (47.7 reps) female FF. Female FF lifted significantly more repetitions than male FF in both age categories. When scores were compared to age and sex stratified normative data, the mean percentile ranking of the old male FF (78%) was significantly greater than the percentile ranking of the young male FF (73%). Again, no differences existed among the percentile rankings of young (86%) and old (88%) female FF. Female FF ranked significantly higher than male FF when compared to normative data in both age categories. Conclusions: Both male and female FF have a high level of upper body muscular endurance. Age has a greater impact on upper body muscular endurance in male FF. Female FF score higher than male FF when the YMCA Bench Press test is used to assess upper body muscular endurance. Practical Applications: Further study in this area is needed to identify whether the age related decrease in muscle endurance observed in male FF is task relevant.