Pulmonary clearance of Tc99m DTPA(PCD) has been used for the measurement of pul-monary epithelial permeability. It, has been reported to be increased not only in variety of pul-monary diseases including ARDS, interstitial fibrosis, and smokers, but also in normal subject,s on posit.ive end expiratory pre,ssure respirator, or after exereise. It was also noted that decrease of pulmonary blood flow due to pulmonary arterial obstruction results in delayed PCD. Normal range of PCD varies with institutes. We prospectively rneasured PCD in 17 normals (5 males and 12 females) consisted of staffs and trainees in the department of radiology of Kangnam St, Marys hospital using original Bark Nebulizer (India). Age ranged from 32 to 43 years. 370 MBq of Tc99m DTPA was inhaled in supine position and supine posterior images were subsequently obtained with 1 min/frame, 64 x 64 matrix and word mode for 30min. Regions of in 1,erest. Were set on each lung, whole lungs, and upper, middle and lower thirds of right lung, respectively. Best fit regression curve was obtained by least square method from inilial 7min after peak act,ivitu on each curve and time for half clearance of maximum activity (tl/2) was calculat,ed. Mean tl/2 was 51 +- 11.2min for whole lung, There was no significant difference between tl/ 2 of right and left lungs, Initial uptake was higher in the lower third and tl/2 was shorter in the lower third than in the upper third(P<0.05). We reviewed several reports on PCD and compared our data with the others. In t,his study, faster clearance in the lower third may be due to the position imaged with or the environment the subject.s belong to, and further invest,igation is under way.