Since previous instances the requirements of environmental, economic and social aspects for all stages of the life cycle of buildings have increased. The criteria of sustainability are included in building environmental assessment systems and tools used in different countries for evaluating the performance of buildings. The purpose of this paper is to introduce the building environmental assessment system (BEAS) which was developed at the Technical University of Ko ice. The Slovak system was developed on the basis of existing systems used in many countries. The indicators were proposed according to available information analysis from particular fields of building performance as well as on the basis of our own experimental experiences. Identification of fields and indicators of assessment is processed by confrontation with foreign approach and conformable with the criteria of building sustainability. After fields and indicators were proposed, they were then weighted using the AHP method. The proposed building environmental assessment system has been verified. Consequently a software tool was suggested for simplification of the process for building performance evaluation.