Summary We have developed specially designed compression immobilizer mede of blistered poly-stylene, to improve the image quality in magnification mammography, especially for mediolateral projection. The evaluated practical benefits of this particular device was as follows : 1. The X-ray absorption by this compresser was minimum, comparing with other devices. There was no detrimental influences on film images produced by this immobilizer. 2. The application in clinical practice was very simple. 3. The motion blurr was thoroughly excluded. 4. The kilovoltages can be lowered due to the evenly decreased thickness of the subjects. Accordingly the diagnostic information volume was significantly increased because of significantly improved X-ray contrast. 5. The glandular structures in dense breast such as of virginal, lactation stages was demonstrable by this compresser. 6. The almost identically dense film opacities were provided both in subareolar and base region. The introduction of this device to the technique in magnification mammography is considered invaluably important.