This study was performed in order to find the effects of kiln size and air fIow rate on the drying quality and duration. it was found that in pine lumber(50 mm thickness), a decrease in air speed From 2,5 m /sec to 1,5 m /sec caused a 7% increase in drying duration to reduce moisture content(M.C) from 40% to 8%. However, the drying quality was the same. In oak lumber(50mm thickness) vvhen the kiln width was increased from 9m to 12meters and the height from 3,3m to 4,2meters, 11% extra drying time was required to decrease the M .C . from 60% to 10%. It was also found that the M .C . distribution was narrower in small sized kiln, but no difference was detected in drying quality caused by kiln size.