The purpose of the study was to evaluate the effects of maximal exercise on the integrity of the alveolar epithelial membrane using the clearance rate of aerosolized ^99mTc-labeled diethylenetriaminepentaacetic acid as an index for the permeability of the lung blood-gas barrier. Ten elite rowers (24.3 ± 4.6 yr of age) completed two 20-min pulmonary clearance measurements immediately after and 2 h after 6 min of all-out rowing (initial and late, respectively). All subjects participated in resting control measurements on a separate day. For each 20-min measurement, lung clearance was calculated for 0-7 and 10-20 min. Furthermore, scintigrams were processed from the initial and late measurements of diethylenetriaminepentaacetic acid clearance. Compared with control levels, the pulmonary clearance measurement after rowing was increased from 1.2 ± 0.5 to 2.4 ± 1.0%/min (SD) at 0-7 min ( P < 0.01) and from 0.8 ± 0.3 to 1.5 ± 0.4%/min at 10-20 min ( P < 0.0005), returning to resting levels within 2 h. In 6 of 10 subjects, ventilation distribution on the lung scintigrams was inhomogeneous at the initial measurement. The study demonstrates an acute increased pulmonary clearance after maximal rowing. The ventilation defects identified on the lung scintigrams may represent transient interstitial edema secondary to increased blood-gas barrier permeability induced by mechanical stress.