The purpose of this study was to examine the effects of exercise upon extravascular lung water as it may relate to pulmonary gas exchange. Ten male humans underwent measures of maximal oxygen uptake in two conditions: normoxia (N) and normobaric hypoxia of 15% O₂ (H). Lung density was measured by quantified MRI prior to and 48.0 ± 7.4 and 100.7 ± 15.1 min following 60 min of cycling exercise in N (intensity = 61.6 ± 9.5 % VO_2MAX), and 55.5 ± 9.8 and 104.3 ± 9.1 min following 60 min cycling exercise in H (intensity = 65.4 ± 7.1 % hypoxic VO_2MAX). VO_2MAX = 65.0 ± 7.5 mL· kg^-1· min^-1 (N), and 54.1 ± 7.0 mL· kg^-1· min^-1 (H). Two subjects demonstrated mild exercise-induced arterial hypoxemia (EIAH) (minSaO₂ = 94.5 & 93.8 %), and 7 demonstrated moderate EIAH (minSaO₂ = 91.4 ± 1.1 %) as measured non-invasively during the VO_2MAX test in N. Mean lung densities, measured once pre- and twice post-exercise, were 0.177 ± 0.019, 0.181 ± 0.019 and 0.173 ± 0.019 g ·mL^-1 (N), and 0.178 ± 0.021, 0.174 ± 0.022 and 0.176 ± 0.019 g·mL^-1 (H). No significant differences (p<0.05) were found in lung density following exercise in either condition, or between conditions. Transient interstitial pulmonary edema did not occur following sustained steady-state cycling exercise in N or H, indicating that transient edema does not result from pulmonary capillary leakage during sustained sub-maximal exercise.