Field data of 53 high dams were comprehensively analyzed to clarify the current conditions of sedimentation in irrigation dams in Japan compared with dams for other purposes. At first, it was shown that the CI ratio was an important index which markedly affected the sedimentation factors, the stages of sedimentation and the trap efficiency. Next, the sedimentation characteristics of the irrigation dams were analyzed and clarified by using the CI ratio. Main results obtained are as follows: (1) The annual sediment deposit rate of irrigation dams is relatively smaller than that of power generation dams in general, implying that the locations of irrigation dams are usually suitable for preventing the occurrence of sedimentation problems. (2) The specific sediment rate of irrigation dams is relatively large in general. Accordingly, it is necessary to investigate the factors which cause the increase of the specific sediment rate rather than the sediment deposit rate in irrigation reservoirs.