The purpose of this study was to examine cardiorespiratory fitness variables and body composition of 5 regular middle-aged swimmers, aged 50-55.The subjects swim almost everyday for the past 8-17 years ((average)x=12.8 yrs.) The comparison had been made between the middle-aged swimmers and nonregular young ex-exercisers that consist of 5 students from a local college, aged 22 in average. Also, data in this research was used to compare with the results found by foreign researchers. Within the limits of this study, the author found that there was no significant difference in vital capacity, predicted Vo2max, heart rate responses to the same work load (75 watts), maximal heart rate, maximal total work, PWC170, and blood pressure during exercise between the middle-aged swimmers and young college students, except for body fat percentage (P＜.01). Furthermore, some variables showed our middle-aged swimmers had better cardiorespiratory fit ness than both sedentary and active people with the same age in other countries. It was concluded that regular swimming participation could make middle-aged people younger than it normally would be in terms of cardiorespiratory fitness.