Summary Rare earth-intensifying screen (LM, LU, G4,G8,GTS, GTH) has been used in our department to decrease x-ray exposure and to improve the film images, in combination with high speed-single emulsion-fine grain film (Low-D). Its clinical significance was evaluated in comparison with conventional film and screen combination. The obtained results were as follows : 1. The overall sensitivities of each combination were RP/TL+HS : RP/TL+LM : RP/TL+LU : Lo-D+LM : Lo-D+LU=1 : 2 : 3 : 6 : 9.5 2. The overall graininess of the combination with rare earth screen showed only slight degrading, comparing with that with conventional screens. 3. The demonstrability of malignant microcalcifications was best in RP/TL+LM, second best in RP/TL+LU and Lo-D+LM. The microcalcifications with 150 microns in diameter can be clearly demonstrated at 25 kVp in those combinations. 4. In clinical practice, Lo-D+LM showed best results, because of its sensitivity and graininess. The standard exposure factors in this combination were 25 kVp, 7 mA, 3 sec, FFD : 70 cm, 2 fold magnification. 5. The skin surface dose in the combination "Lo-D+LM" was 430 mR which is one third of conventional method. In conclusion, "Lo-D+LM" combination is considered to be most recommendable for magnification mammography technique.