Though increasing age and body weight (BW) have been widely known to be associated with slower distance run times, the common convention in 5K road races is to categorize competitors by age and, sometimes, BW. This has the disadvantage of assigning only small numbers of competitors to age categories and giving advantage to runners close to the minimum age or BW values allowable. Using recent advances in the modeling of distance run performance by BW combined with empirical evidence quantifying the independent effect of age on cardiovascular endurance, we previously published the derivation of the 5K Handicap (5KH), an age and BW handicap model for the 5K road race. With the inputs of age, BW and actual run time, the 5KH computes an adjusted run time which can be used to compare runners of different age and BW within the same gender. In this study, we field tested the 5KH in two local races with 275 men and 126 women. Results suggest that the 5KH eliminates the age and BW bias, and may provide more incentive for older and heavier runners to compete. Furthermore, the BW bias in the 5K tended to be lower for women than for men. The first scientifically-based age and BW graded system, the 5KH appears valid for both genders and may have application for other race distances and fitness testing environments.