Pruning of long season, high-wire supported tomato plants is a commonly commercial operation, involving removing the older leaves from the lower part of the stem (deleafing) and lowering the plant height.This action has generally been attributed to accelerating fruit ripening, exposing the truss for easier harvest and preventing foliage diseases.Yet, the steeply reduced leaf area caused by pruning may have a significant impact on air temperature and its spatial distribution and on other environmental factors, which may in turn affect plant physiology.To determine the effect of leaf pruning and lowering crop height on air temperature, experiments were done in a flat-roof screenhouse,4 m in height, with a floor area of 745 m2, in which tomato plants were gown.The screenhouse was ventilated thorough the roof which was covered by a fine mesh insect-proof screen.The screenhouse sidewalls were covered by impermeable polyethylene sheets.Air temperature was measured at the center of the screenhouse at six different heights.The results show that after pruning the air temperature was higher than before pruning.Both before and after pruning the screenhouse air temperature was most of the time cooler than external air temperature.Temperature gradients above 1.7 m from the ground were smaller after than before pruning.