The effectiveness of the extended-cycle process, in which processing time is longer than the manugacturer's recommendation, was investigated using four mammographic films, Konica New CM, Fuji UM-MA HC, Kodak Min-R 2000, and Kodak Min-R M, Fuji UR-2, a double-emulsion film, was used as a control. The sensitometric strips exposed by a sensitometer were processed in different combinations of developing temperatures ranging from 28 to 36℃, processing times from 45 to 210 sec chemicals, Konica XD-90C, Fuji RD-5 and Kodak RP X-Omat. Those characteristics(average gradient, relative speed, base plus fog)obtained from characteristic curves were evaluated for the different developing temperatures, times and chemicals. Fuji UR-2 was scarcely affected, while mammographic films were greatly affected in the different combinations without an increase in base plus fog. For New CM, UM-MA HC and Min-R M, the average gradient and relative speed increased as developing temperature increased and developing time was extended, but the increases were limited with the combination of 36℃ and 210 sec for New CM and UM-MA HC. For Min-R 2000, the average gradient was almost constant, and the relative speed increased like the other three mammographic films. Changes in average gradient and relative speed due to chemical variations showed increases or decreases from 6% to 9% compared with Konica chemical. These results suggested that the extended-cycle process for the above mammographic films has the possibility to contribute to dose reduction and advancement of contrast on mammography.