The ecological building design is a response to environmental pollution caused by construction activity. Such design of buildings takes into account environmental problems and strives toward preserving ecological balance, while at the same time attempting to meet requirements for a healthy and comfortable living. Ecologically sustainable design measures are examined in the paper. A preliminary design of an ecological building named Gazi University Environmental Research and Training Laboratory (GUERTL) in Ankara, is analysed. According to the suggested evaluation method, the ecological performance of the building, i.e. the success rate of the design, amounts to 88 %.