BACKGROUND It is possible that different forms of locomotion, when carried out at the same speed, may have a distinct influence on the physiological and perceptual responses to exercise. OBJECTIVE To compare the cardiorespiratory responses and the subjective perception of the effort to walk and run at the same speed, as determined from the walk-run transition speed (WRTS). METHODS From an initial sample of 453 subjects enrolled in the compulsory military service, 12 young adult men were selected and carefully homogenized as to age, sex, anthropometric characteristics, aerobic condition and experience in a treadmill. In preliminary sessions, the individual WRTS was determined. Thereafter, on three different days, the subjects walked and ran in balanced order, in each of the following speeds: WRTS; WRTS - 0.5 km/h; WRTS + 0.5 km/h, so as to obtain exhaled gases, heart rate (HR) and perception of effort measurements. RESULTS The protocol for WRTS detection was highly reproducible (r = 0.92, p <0.05). In an intensity of exercise above the WRTS, the perceived effort, the HR, and the ventilatory variables-VE, VO2, VCO2 and R-showed higher values during walking than during running (p <0.05), whereas at the WRTS and at the speed of 0.5 km/h below WRTS, the form of locomotion did not affect the cardiorespiratory and perceptual variables (p > 0.05). CONCLUSION Walking at a speed above the WRTS tends to be more stressful to the subject, from a physiological and perceptual point of view. It seems appropriate to individualize the WRTS and standardize the form of locomotion for determining a more accurate and physiological intensity of the aerobe exercises.