The purpose of this study was to assess the validity of predicting the maximal oxygen uptake ((V)over dot O(2max)) of sedentary men from sub-maximal (V)over dot O(2) values obtained during a perceptually regulated exercise test. Thirteen healthy, sedentary males aged 29-52 years completed five graded exercise tests on a cycle ergometer. The first and fifth test involved a graded exercise test to determine (V)over dotO(2max). The two maximal graded exercise tests were separated by three sub-maximal graded exercise tests, perceptually regulated at 3-min RPE intensities of 9, 11, 13, 15, and 17 on the Borg ratings of perceived exertion (RPE) scale, in that order. After confirmation that individual linear regression models provided the most appropriate fit to the data, the regression lines for the perceptual ranges 9-17, 9-15, and 11-17 were extrapolated to RPE 20 to predict (V)overdotO(2max). There were no significant differences between (V)over dot O(2max) values from the graded exercise tests (mean 43.9ml.kg(-1).min(-1), s=6.3) and predicted (V)over dot O(2max) values for the perceptual ranges 9-17 (40.7ml.kg(-1.)min(-1), s=2.2) and RPE 11-17 (42.5ml.kg(-).min(-1), s=2.3) across the three trials. The predicted (V)overdot O(2max) from the perceptual range 9-15 was significantly lower (P<0.05) (37.7ml.kg(-1).min(-1), s=2.3). The intra-class correlation coefficients between actual and predicted (V)overdot O(2max) for RPE 9-17 and RPE 11-17 across trials ranged from 0.80 to 0.87. Limits of agreement analysis on actual and predicted (V)overdot O(2) values (bias +/- 1.96sdiff) were 3.4ml.kg(-1).min(-1) (+/- 10.7), 2.4ml.kg(-1).min(-1) (+/- 9.9), and 3.7ml.kg(-1).min(-1) (+/- 12.8) (trials 1, 2, and 3, respectively) of RPE range 9-17. Results suggest that a sub-maximal, perceptually guided graded exercise test provides acceptable estimates of (V) overdotO(2max) in young to middle-aged sedentary males.