There is a paucity of research examining the 6-minute walk test (6MWT) in young to middle-aged healthy individuals, and little is known about the utility of the 6MWT for predicting aerobic fitness. Purpose: 1) To characterize the aerobic demand of the 6MWT in a group of healthy working-aged adults; 2) to examine the ability of the 6MWT to objectively differentiate the fitness level between participants; and 3) to create prediction equations for 6MWT distance and maximal oxygen consumption (VO 2 max) using the 6MWT results in combination with easily measured anthropometric and demographic variables. Methods: Participants (N = 44; men, 23; women, 21) completed the 6MWT, VO 2 max, and a battery of simple fitness measures. Results: The aerobic demand of the 6MWT was 28.7 ± 5.7 mL·kg -1 ·min -1 (72.7% ± 11.6% of VO 2 max). Rank order correlation revealed a moderate strength association between 6MWT distance and VO 2 max (r = 0.49; P = 0.001). Using stepwise multiple linear regression, we were able to account for 72.4% of the variance in VO 2 max using the 6MWT when combined with participant body weight, sex, resting heart rate (HR), and age according to the following equation: VO 2 max (mL · kg -1 · min -1 ) = 70.161 + (0.023 × 6MWT m) - (0.276 × weight kg) - (6.79 × sex, where m = 0, f = 1) - (0.193 × resting HR beats per minute) - (0.191 × age y). Conclusion: The 6MWT is of moderate-to-vigorous intensity, and may be useful in the classification of aerobic fitness, which is associated with health outcomes. Inclusion of further patient characteristics greatly increases the predictive value of the 6MWT for estimating VO 2 max, which has important implications for those seeking a noninvasive and simple-to-use determinant of maximal aerobic power.