A research project aimed to determine heating and cooling potential of the aquifer thermal energy storage (ATES) system in the Mediterranean climatic zone greenhouses was carried out in Cukurova University, Adana during 2005-2006. For these purposes, two plastic greenhouses, each having an area of 360 m(2), have been used. One of them was heated and cooled by ATES technique. In the second one conventional heating and cooling systems has been used. Outside and greenhouses inside temperatures as well as ground water and exchanger water temperatures were recorded during whole experimental period. Tomato crop was grown in both greenhouses and plant growth and fruit yield were measured. Energy costs of the greenhouses (fuel oil for conventional heated and electricity for ATES) were also calculated. Consequently, these two systems were technically and economically compared.