Under Greek, Athens region, summer conditions and with no misting, pigs are subjected to heat stress of considerable duration and intensity. Transient simulations were conducted using an extension of the AGRISIM program to study three different cases in a growing swine building: (1) no misting, (2) misting up to a relative humidity of 65% and (3) misting up to a relative humidity of 80%. A 30-year data set of real hourly weather data was used. The amount of misting water per hour required was calculated using a new control strategy and found not to exceed 0.8 kg h'1 pig'1. The simulations confirm that pigs are subjected to heat stress and that this can be reduced substantially when misting is used. More specifically, misting up to an inside relative humidity of 80% is justified during July and August, while an upper limit of 65% is reasonable for May, June and September.