One-hundred-sixteen healthy subjects (60 female and 56 male) with normal height (L) and weight (w) were selected to provide an even distribution of age (A, 20-70 years). All underwent an unsteady state cycle ergometer test with work increments of 20 watts each minute to exhaustion. A commercially available exercise testing system (EOS SPRINT, Jäger Corp., FRG) with gas analysis from a mixing chamber was used to study oxygen uptake (VO2), carbon dioxide output (VCO2), heart rate (HR), tidal volume (VT), breathing frequency (BR) and arterial oxygen tension (PO2) with special regard to the ventilatory anaerobic threshold (VAT) and maximum power output. For all parameters multiple regression equations were determined. Furthermore, heart rate reserve (HR-reserve), breathing reserve (VE-reserve), O2-pulse (VO2/HR), the dead space/tidal volume ratio (VD/VT) and the alveolar-arterial PO2-difference (AaDO2) were calculated. Day-to-day reproducibility was proven in 21 subjects. VO2max in females was 1584 +/- 300 ml/min (VO2max = -17 A + 10 L + 10 G + 58, r = 0.75, p < 0.0001), VO2AT 957 +/- 159 ml/min (VO2AT = 0.35 VO2max + 0.40 l/min, r = 0.77, p < 0.0001). The ratio VO2AT/VO2max was 50 +/- 7%. In male, VO2max was 2452 +/- 529 ml/min (VO2max = -23 A + 23 L + 9.5 G - 1395, r = 0.78, p < 0.0001), VO2AT 1209 +/- 213 ml/min (VO2AT = 0.29 VO2max + 0.51 l/min, r = 0.71, p < 0.0001), and VO2AT/VO2max 62 +/- 9%.(ABSTRACT TRUNCATED AT 250 WORDS)