The main purpose of the present study was to identify some of personality factors influencing perceived exertion responses under two different exercise conditions. Fifty male university students were required to pedal a bicycle ergometer at 50 rpm during l0 and 30 minutes-exercise periods. The order of the exercise presentation was counterbalanced and each exercise wan administered on separate days with one week interval. The ratings of perceived exertion which consist of central and local factors were conducted at each heart rate index point (heart rate during exercise/heart rate after one minute exercise) under the two exercise conditions. As the predictor variables for the perceived exertion, California Psychological Inventory (CPI) was employed and administered two weeks before the experiment. The data were analyzed by use of a multiple regression technique. The main results were summarized ad follows: 1. Contribution of the personality factors to the perceived exertion responses was relatively small under both l0 and 30 minutes-exercise conditions. The contribution under 30 minutes-exercise condition, however, was relatively larger than under l0 minutes-exercise condition. 2. Under 30 minutes-exercise condition, Social Presence factor of CPI was extracted from the multiple regression analyses as a first predictor variable for almost heart rate index points. The factor had larger contribution to the perceived exertion responses than other CPI factors. 3. Concerning the contribution of personality factors to the perceived exertion responses, there were no distinct differences between the central and local factors.