The purposes of this study were 1) to describe a maximal aerobic capacity (MAC) test and 2) to report on its reliability. Thirty subjects (16 males and 14 females) were tested for maximal aerobic power (MAP) with a progressive bicycle ergometer test and the ventilatory anaerobic threshold (VANT) was determined. MAC was measured as the amount of work that could be performed in 90 min on a bicycle ergometer at an intensity set individually from VANT. Subjects were asked to perform as much work as possible during this non-stop 90 min period. For females and males respectively, MAP reached 42.9 +/- 5.9 (mean +/- SD) and 56.0 +/- 4.7 ml O2/kg X min-1 (p less than .01), VANT 36.3 +/- 6.1 and 46.0 +/- 5.2 ml O2/kg X min-1 (p less than .01), max HR 198 +/- 8 and 195 +/- 9 (p greater than .05) and HR at VANT 187 +/- 9 and 180 +/- 10 (p greater than .05). The same subjects were tested twice for MAC within 7 days. Results expressed in kJ/kg reached 10.6 +/- 2.1 and 10.8 +/- 2.4 for females, 14.7 +/- 2.1 and 14.9 +/- 2.2 for males. Mean HR maintained during MAC were 174 +/- 11 and 174 +/- 9 for females and 169 +/- 10 and 170 +/- 10 for males. There was a non significant difference between means (p greater than .05) of the first and second test in total work performed in kJ/kg. This difference reached about 2% of the first test score, 32.7% of this difference occurring in the first 10 min.(ABSTRACT TRUNCATED AT 250 WORDS)