[en] The combination of mean circulation time (MCT) and the slope (A) of the straight line (Y = AX + C) fitted to the initial part of the time activity curve as K = A: sufferd leg / A: normal leg x 1/MCT: sufferd leg / 1/MCT: normal leg sharply reflected the difference of the time activity curve between a suffered leg and a normal leg. In this formula it is devised to exclude the elements (the method for injection of Technetium-99m and cardiac function) reflecting to the time activity curve.FFifteen cases of chronic peripheral arterial disease and fifteen normal subjects as control were investigated using RI-angiography before and after operation.FAnalysis of K value was effective for diagnosis when the suffered leg was one side, however, this method had a problem, when the both legs were suffered as Leriche syndrome. The K value of the femoral arterial region resulted to reflect the nature of occluded artery more accurately than the region of iliac artery. The case suffered from the obstruction of artery on one leg showed K value lower than 0.7, while the K value of normal leg was around 1.0. Moreover, the case whose K value approaches to 0.7 has a slight obstruction of the artery, suggesting to have some blood supply from co-lateral arteries. In clinical study, the patients with higher K value had the tendency to be better in prognosis after the operation. Thus, it seems to be effective to analyse the time activity curve of RI-angiography for the screening examination before operation for the observation of the progress or especially for the evaluation of the effectiveness of the operation performed