There is a demand for production of temperate vegetables in the tropics and subtropics. When vegetables are grown at high temperatures, though, they experience heat stress, and high-temperature injury occurs during production. High-temperature injury can be caused by short-term stress, for example temperatures exceeding 40 ℃, as well as by mild long-term or chronic heat stress. Farmers do not cultivate vegetables in areas where the crop dies at high temperatures, for example above 40 ℃, but in agriculture, chronic heat stress is a problem even at temperatures slightly above optimal. In this report I describe the production of heat injury in green bean (Phaseolus vulgaris) under chronic mild heat stress, and high-temperature control technologies for greenhouses in summer in Japan.