BACKGROUND: Although graded exercise stress tests are widely used for the evaluation of cardiorespiratory performance, normal standards on respiratory gas exchange and ventilatory functions at maximal exercise in Koreans have not been well established. The purpose of this study is to provide reference values on these by sex and age, along with derivation of some of their prediction equations. METHOD: Symptom-limited maximal exercise test was carried out by Bruce protocol in 1,000 healthy adults consisting of 603 males and 397 females, aged 20~66 years. Among them VC, FEV1 and MVV were also determined in 885 cases. All the subjects were members of a health center, excluding athletes. During the exercise, subjects were allowed to hold on to front hand rail of the treadmill for safety purpose. RESULTS: The VO2 max/m2, VCO2 max/m2 and VE max/m2 were greater in males than in females and decreased with age. The RR max in men and women was similar but decreased slightly with age. The VT max was markedly greater in men but showed no significant changes with age in either gender. The mean of VT max/VC, VE max/MVV and BR revealed that there were considerable ventilatory reserves at maximal exercise even in older females. The regression equations of the cardinal parameters obtained using exercise time(ET, min), age(A, yr), height(Ht, cm), weight(W, kg), sex(S, 0=male; l=female), VC(L), FEV1(L) and VE max(L) as variables are as follows: VO2 max/m2(L/min)=1.449+0.073 ET-0.007A+0.010W-0.006Ht-0.209S, VCO2 max/m2(L/min)= 1.672+0.063ET-0.008A + 0.010W -0.005Ht -0.319S, VE max/m2(L/min)=58.161 +1.503ET - 0.315A-9.871S or VE max/m2(L/min)=47.873+6.548 FEV1-5.715 S, and VT max(L)=1.497+ 0.223VC-0.493S. CONCLUSION: Respiratory gas exchange and ventilatory variables at maximal exercise were studied in 1,000 non-athletes by Bruce protocol. During exercise, the subjects were allowed to hold on to hand rail of the treadmill for safety purpose. We feel that our results would provide ideal target values for patients and healthy individuals to be achieved, since our study subjects were members of a health center whose physical fitness levels were presumably higher than ordinary population.