string: The benthic macroinvertebrates of Lake Yamanakako have been studied by various researchers (Miyadi 1932; Kitagawa 1973; Yasuno et al. 1983). We compared our results with previous data on chironomids and oligochaetes reported by Miyadi (1932) and Kitagawa (1973) and tried to clarify the relationship between the eutrophication of Lake