Maximal aerobic power was measured on 180 non-athletic and athletic men, using a treadmill walking method (Modified Balke's). The following equations were obtained in the present study : For non-athletic men (ages 20 to 72 yr); Maximum ventilation (1/min) =100.4-0.719 age (yr.). Aerobic power (1/min) =3.02-0.0186 age (yr.). Aerobic power per kg of body weight (ml/kg. min) = 49.88 - 0.3019 age (yr.). Maximum heart rate (beats/min) = 201.7 - 0.583 age (yr.). For athletic men, ages 30 to 72 yr. : Maximum ventilation (1/min) = 129.3-1.042 age (yr.). Aerobic power (1/min)=4.51-0.0347 age (yr.). Aerobic power per kg of body weight (ml/kg. min)=61.57-0.2747 age (yr.). Maximum heart rate (beats/min) = 208.0 - 0.706 age (yr.). Aerobic power (1/min) of athletic men was greater than that of non-athletic men by 40.2% in 40s and 60s, 25.7% in 30s and 16.9% in 50s. Aerobic power per kg of body weight (ml/kg. min) was greater than that of non-athletic men by 60% in 60s, 35-38% in 40s, 50s and 70s. The inclination of regression line of aerobic power (ml/kg. min) to age was similar each other between athletic and non-athletic men. The subjects over 30 years old were classified into 4 groups (Groups A, B, C, D) based on the running distance and frequency of their usual training. Aerobic power of Group-A (5-16km running every day) averaged 3.67 1/min (59.9ml/kg. min) for 30s, 2.98 1/min (50.4ml/kg. min) for 40s, 2.51 1/min (49.8ml/kg. min) for 50s and 2.56 1/min (50.1ml/kg. min) for 60s. These values were greater than that of Group-D (sedentary) by 133% in 60s and 68-27% in 30s to 50s. The greatest individual values of aerobic power for each age group were 57. 0ml/kg. min in 40s, 58.7ml/kg. min in 50s, 57.9ml/kg. min in 60s and 38.8ml/kg. min in 70s. These valued are similar with that of Caucacian middle-old aged athletes.