Judicious control of high temperature is the most important task for a successful intensive - cultivation in greenhouses during the hot summer. Therefore, the climatological data at 31 locations in Korea were calculated using the modified model equation for ventilated in glasshouses during summer. Furthermore, the adequate number of air- changes or frequency of ventilation was estimated based on temperature settings, which is considered to be more active means of controlling summer glasshouse temperatures, was investigated. The major results can be summarized as follows: Forced ventilation of one air change per minutes was effective in maintaining the maximum air temperature below 35$^{circ}C$ in the glasshouse haying 40% shading. It was impossible, however, to maintain air temperature below 3$0^{circ}C$ in 40% shaded glasshouse with forced ventilation only.