The role of posterior vitreous detachment in the formation of idiopathic macular hole was evaluated in 310 eyes. The eyes were classified according to the stage of the initial macular pathology: group 1, macular cyst; group 2, early macular hole; and group 3, fully developed macular hole. The initial prevalence of posterior vitreous detachment was 0% (none of 15 eyes) in group 1, 6% (three of 50 eyes) in group 2, and 27% (67 of 245 eyes) in group 3. During the study, all 15 eyes in group 1 and all 43 eyes in group 2 for which data were obtained progressed to fully developed macular holes without the occurrence of posterior vitreous detachment. The findings strongly suggested that most idiopathic macular holes develop in the absence of posterior vitreous detachment and that the pathogenesis of the holes may be independent of the occurrence of posterior vitreous detachment.