Abstract We aimed to characterize intravitreal membranes in dogs and determine, if possible, associated predisposing conditions. Five globes in which intravitreal membranes were identified were evaluated. These originated from four Labrador Retrievers or Labrador-cross dogs and a Springer Spaniel. The ages of the dogs ranged from 4 to 11 years. Standard histology and immunohistochemical procedures for factor VIII-related antigen, smooth muscle actin (SMA), vimentin and glial fibrillary acidic protein (GFAP) were performed. Intravitreal membranes varied from loosely to highly organized. The extent of organization corresponded with increasing immunoreactivity for vimentin and GFAP, indicating their predominantly glial origin. They were never immunopositive for smooth muscle actin, nor were they vascularized. In all cases, they were associated with intravitreal hemorrhage. Additional common findings included epiretinal membranes, retinal neovascularization, preiridal fibrovascular membranes and glaucoma. Intravitreal membranes may be a sequelae of intravitreal hemorrhage. This in turn, may arise from new vessels associated with epiretinal or preiridial membranes, or hemorrhage associated with optic disc cupping or retinal neovascularization. All of these phenomena may accompany glaucoma.