BACKGROUND: The operating room should provide an optimum environment that is safe for the patient and the working personnel. In this point of view, we investigated 8 items of temperature, humidity, air flow, noise, brightness, dust, CO2 and NO2. METHODS: Operating rooms, corridors and recovery rooms were tied as region I, II and III depending on their characteristics. 29 points were measured using appropriate instruments. After that, averaged values were calculated. RESULTS: Indoor climate (temperature, humidity and air flow) in region I were averaged 24.7, 65, 0.18/II were 25.5, 68, 0.18/III were 22.3 (degrees C), 56 (%), 0.22 (m/sec). Physcial condition (noise, brightness and dust) in region I were averaged 63, 295, 63/II were 67, 138, 87/III were 63 (db), 139 (lux), 26 (microgram/m3). Harmful gas (CO2 and NO2) concentration in region I were averaged 1152, 0.008/II were 913, 0.009/III were 1367 (ppm), 0.013 (ppm). CONCLUSIONS: Temperatures were appropriate but humidities were high except partial points. Air flow showed low values in average. Values of noise, dust and CO2 were relatively high. NO2 was low but brightness was variable. These mean that adequate improvement for quiet condition and air ventilation should be considered.