Introduction Educational environment is an important factor in effective teaching and learning. Positive educational environments result in better academic achievements. Administrators are responsible for education at the department and faculty levels, and attention is given to the educational atmosphere by regularly measuring and evaluating various related factors including the subjective level of awareness and perception of residents. A teaching and learning system should include learning and environment assessment tools to allow residents to take good care of patients. Many educational environment assessment tools have been created to assess the quality of educational environments. Examples include the Dundee Ready Education Environment Measure (DREEM) with 50 items, 1,2 the Postgraduate Hospital Education Environment Measure (PHEEM) with 40 items 3-7 and the Anesthetic Trainee Theatre Educational Environment Measure (ATEEM) with 40 items. 1,8,9 Anesthesiology is a fundamental branch of medicine. There are specific tools for different disciplines that are used only for each study group. These have a variance in the measurement of psychological quality (psychometric) but are considered the best basic tools for easy measurement. In 2004 Holt and Roff 1 developed the ATEEM, a standardized tool used to assess the perception of the educational atmosphere among anesthesiology residents. Medical schools in many countries have endorsed its use in the assessment of educational environments. At present, ATEEM has not yet been translated into Thai. This research is therefore a good starting point for systematically enhancing the strengths and improving the weaknesses of the educational atmosphere in the Department of Anesthesiology using ATEEM (Thai version). The researcher has chosen this tool to measure the level of perception of anesthesiology residents in their