The purpose of this study was to assess the validity of predicting maximal oxygen uptake ( [(V)\dot]\textO_\text2max )\left( {\dot V{\text{O}}_{{\text{2max}}} } \right) from sub-maximal [(V)\dot]\textO_\text2\dot V{\text{O}}_{\text{2}} values elicited during a perceptually-regulated exercise test. We hypothesised that the strong relationship between the ratings of perceived exertion (RPE) and [(V)\dot]\textO_\text2\dot V{\text{O}}_{\text{2}} would enable [(V)\dot]\textO_\text2max\dot V{\text{O}}_{{\text{2max}}} to be predicted and that this would improve with practice. Ten male volunteers performed a graded exercise test (GXT) to establish [(V)\dot]\textO_\text2max\dot V{\text{O}}_{{\text{2max}}} followed by three sub-maximal RPE production protocols on a cycle ergometer, each separated by a period of 48 h. The perceptually-regulated trials were conducted at intensities of 9, 11, 13, 15 and 17 on the RPE scale, in that order. [(V)\dot]\textO_\text2\dot V{\text{O}}_{\text{2}} and HR were measured continuously and recorded at the end of each 4 min stage. Individual [(V)\dot]\textO_\text2max\dot V{\text{O}}_{{\text{2max}}} (48.8 ml·kg^–1·min^–1) and predicted [(V)\dot]\textO_\text2\dot V{\text{O}}_{\text{2}} max values (47.3, 48.6 and 49.9 ml·kg^–1·min^–1, for trials 1, 2 and 3, respectively) when [(V)\dot]\textO_\text2\dot V{\text{O}}_{\text{2}} max was predicted from RPE values of 9–17. The same was observed when [(V)\dot]\textO_\text2max\dot V{\text{O}}_{{\text{2max}}} was predicted using RPE 9–15. Limits of agreement (LoA) analysis on actual and predicted [(V)\dot]\textO_\text2max\dot V{\text{O}}_{{\text{2max}}} values (from RPE 9–17) were (bias±1.96×SDdiff) 1.5±7.3, 0.2±4.9 and –1.2±5.8 ml·kg^–1·min^–1, for trials 1, 2 and 3, respectively. Corresponding LoA values for actual and predicted [(V)\dot]\textO_\text2max\dot V{\text{O}}_{{\text{2max}}} (from RPE 9–15) were 5.4±11.3, 4.4±8.7 and 2.3±8.4 ml·kg^–1·min^–1, respectively. The data suggest that a sub-maximal, perceptually-guided, graded exercise protocol can provide acceptable estimates of maximal aerobic power, which are further improved with practice in fit young males.