Window setting is a very important technique in CT examinations. However, most beginner technologists have difficulty in setting the optimal window. Now, thanks to technical progress, it is easy to obtain a great many CT images. On the other hand, it is impossible to provide the optimal window setting for all images. Therefore, our purpose is to offer optimal CT images for every patient by using the automatic window-level and width-setting system. As a result of this experiment, there was a considerable difference in window setting by an expert technologist and that by a beginner technologist. With our system, we were able always to obtain an optimal window setting, such as that set by an expert technologist, regardless of the CT experience of the radiological technologist. We think that this system will be effective in observing animated examinations even if film is no longer used in the future.