Pulmonary diffusion capacity has been observed to be reduced by approximately 14% 2h after 4-6 min of maximal exercise. The purpose of this study was to determine if the decrease in pulmonary diffusion capacity also occurs when the duration of exercise intensity is shorter or when the exercise intensity is lower. We measured pulmonary diffusion capacity using the single breath method in 12 competitive rowers 22 (16-31) years old, 70 (56-100) kg body weight, and 180 (171-193) cm body height under two conditions: (1) 2h after 6 min of rowing at both 61% (58%-68%) and 76% (73%-78%) of maximal oxygen uptake; (2) 2h after 1, 2, or 3 min of all-out rowing. Values are presented as medians with ranges. Pulmonary diffusion capacity was reduced by 6% (2%-17%) after 6 min of rowing at 61% and by 10% (-7%-21%) after 6 min of rowing at 76% of maximal oxygen uptake (p < 0.03). Pulmonary diffusion capacity was reduced by 7% (3%-19%), 8% (2%-17%) and 7% (1%-16%) after 1, 2, and 3 min of all-out rowing (p < 0.01). We conclude that submaximal exercise at 61% of maximal oxygen uptake will affect pulmonary diffusion capacity following exercise as will shorter duration of maximal exercise. Although the mechanism for this fall in pulmonary diffusion capacity is unclear, the fact that it occurs after even mild exercise makes a significant change in pulmonary capillary membrane integrity or subclinical pulmonary edema unlikely.(ABSTRACT TRUNCATED AT 250 WORDS)