[en] We applied an extended-cycle process, in which the processing time is longer than the manufacturer's recommendation, to a low-speed, high-resolution system in mammography and investigated to what extent sharpness, contrast, and speed would be maintained or increased and whether this process could be applied clinically. In this study, a single-screen/single-emulsion film, Konica M-100/CM-H, was used in the low-speed, high-resolution system, and M-200/CM-H was employed for comparison. Developing temperatures of 30, 32, and 34 degrees centigrade and a processing time of 210 seconds were selected as conditions of the extended-cycle process. M-100/CM-H with the extended-cycle process (M-100/E system) and M-200/CM-H with the standard-cycle process were compared at 34 and 90 seconds (M-200 system) in terms of contrast, speed, modulation transfer function (MTF), and Wiener spectrum (WS). In addition, the visibility of mammograms obtained using an RMI 165 phantom was evaluated by the method of paired comparisons. In the comparison of the M-200 system with the M-100/E system at 34 and 210 seconds, the speed was almost equal and the average gradient and MTF value at 2.5 cycles/mm increased about 20% and 8%, respectively. WS was higher due to the increase in quantum mottle with increases in the average gradient and MTF. In the scale of the method of paired comparisons, M-100/E systems showed better results. Moreover, entrance skin exposure in air of the M-100/E system at 34 and 210 seconds was almost equal to that of the M-200 system. These results suggested that it was possible to improve visibility by the extended-cycle process in a low-speed, high-resolution system. (author)