The purpose of this study was to clarify the validity of 12-min submaximal treadmill walk (TMW) and run (TMR) tests, as indirect measures of cardiorespiratory endurance, and to develop estimation equations of cardiorespiratory endurance using TMW or TMR performance and some other useful items correlating with cardiorespiratory endurance. Fifty-one young adult men, aged 20 -r34 years (22.8±3.6), walked or ran for 12 minutes on the treadmill at the intensity corresponding to the level 13 on the Borg's ratings of perceived exertion (RPE 13), and performed a maximal incremental exercise test. Mean (± SD) of oxygen uptake corresponding to anaerobic threshold (VO₂AT) and maximal oxygen uptake (VO₂max) were 42.0 ± 9.0 ml/kg/min and 55.9 ± 7.4 ml/kg/min, respectively, and mean (± SD) of 12-min walk and run distances were 1221 ± 103 m and 2108 ± 269 m, respectively. Cardiorespiratory endurance indices (VO_2AT and VO₂max) significantly correlated with TMW (r=0.49 and 0.48, respectively) and with TMR (r=0.69 and 0.68, respectively) . A stepwise multiple regression analysis was applied to determine the estimation equations of the cardiorespiratory endurance using VO_2AT or VO₂max as a dependent variable, and TMW or TMR distance, age, resting heart rate (HRrest), and exercise frequency in a week as independent variables. The multiple regression equations of VO_2AT and VO₂max were developed as follows : When TMW distance entered as an independent variable, VO_2AT = 20.781 X₁ + 2.298 X₃ - 0.29 X₄ + 31.855 (r = 0.83, SEE = 5.33 ml/kg/min) : VO₂max =19.941 X₁ + 1.127 X₃ - 0.208 X₄ - 0.656 X₅ - 0.853 X₆ + 77.884 (r = 0.88, SEE = 3.96 ml/kg/min), and when TMR distance entered as an independent variable, VO₂AT =15.443 X₂ + 2.158 X₃- 0.157 X₄ + 14.234 (r = 0.90, SEE = 4.18 ml/kg/min) ; VO₂max =10.817 X₂ + 1.274 X₃ - 0.1946 X4 - 0.504 X₅ + 55.234 (r = 0.89, SEE = 3.79 ml/kg/min), where X₁ : TMW distance (m), X₂: TMR distance (m), X₃ : exercise frequency in a week (d/wk), X₄: HRrest (b/min), X₅: age (yr) and X₆: BMI. It is concluded that cardiorespiratory endurance could be better estimated by a combination of submaximal exercise performance and some easily measurable items correlating with cardiorespiratory endurance such as exercise frequency, circulatory function, chronological age and body composition.