Differentiated ratings of perceived exertion (RPE) were obtained from eight low-altitude residents during cycle exercise at sea level (SL) and after acute (< 2 h) and chronic (18 d) exposure to high altitude (4,300 m; HA). Mean Vo2max, was 27% lower with acute HA exposure than at SL and was not significantly changed with chronic exposure. Subjects cycled for 30 min at an exercise intensity requiring 85% of Vo2max. Respiratory exchange measurements and differentiated RPE were obtained at minutes 5,15, and 25 of exercise, and pre-and post-exercise blood samples were collected. Differentiated RPE included a local muscular rating, a central or cardiopulmonary rating, and an overall rating. Despite reduced absolute exercise intensity during acute HA exercise, local RPE were unchanged from SL values. Chronic HA exercise, however, was associated with a significant reduction in local RPE. Blood lactate accumulation during SL exercise was not significantly different from acute HA exercise but was significantly less during chronic HA exercise. At SL, local ratings were significantly greater than central ratings, while neither differed significantly from the overall ratings. None of the differentiated ratings differed significantly during acute and chronic HA exercise; central RPE were highest of the ratings during chronic HA exercise. The ventilatory equivalent for oxygen during HA exercise (both acute and chronic) was significantly higher than at SL. This apparent rearrangement in the relative order of magnitude of these three differentiated ratings suggests an alteration in the relationship between perceptual cues sensed as effort.