The survey of the parameters of diagnostic X-ray apparatus, that is, tube voltage, tube current and exposure time, was carried out. The nominal parameters chosen were 70kV, 200mA and 0.1s. Forty-seven institutions were visited, using a total of 63 machines. Most devices meet the JIS for the voltage (±7% to the nominal value) and exposure time (±10%). As for the current, 19 (30.2% of all) devices were out of the JIS (±10%). No significant differences were found between the rectifying methods. If the specific dose (mGy/mAs) is estimated by the nominal parameters, the error of the dose would be 20 to 30%. The quality assurance of the device is very important for the optimization of medical exposure.
