We studied the relationship between hemispheric asymmetry, emotion, and aerobic exercise intensity. Nine participants used a bicycle ergometer to exercise for 2 15-minute periods at 2 different exercise intensities : a comfortable self-established pace (CSEP) and 70%VO₂ max. CSEP was defined as exercise intensity that the subject subjectively determined to be comfortable. Electroencephalograms (EEG) were monitored prior to exercise and during exercise recovery. To evaluate emotional changes associated with exercise, questionnaires were completed prior to, during, immediately after exercise and during exercise recovery. The α-power spectrum of the frontal EEG was classified as follows : α 1, 8-9.5 Hz; a 2, 9.5-11.5 Hz; and α 3, 11.5-13 Hz, and compared at F3 to F4 for each α-power spectrum. Both exercises at CSEP and 70%VO₂max intensity showed decreased anxiety between immediately after exercise and during exercise recovery. Duration, rise, and fall of positive emotion and relaxation differed between exercise intensities. Exercise at CSEP intensity was not hemispherically asymmetric prior to exercise and during recovery. Exercise at 70 %VO₂ max was not hemispherically asymmetric prior to exercise, however, the α 2 power of F3 was lower than that of F4 during 60-minute recovery. The left frontal α-power spectrum, specially a 2, at 70%VO₂ max would reflect increased positive emotions and decreased anxiety during exercise recovery. These results are discussed based on the approach-withdrawal model of Davidson.