Fifty vitreous specimens obtained by routine pars plana vitrectomies were examined using Millipore filter processing and Papanicolaou staining technique. Cytological findings comprised of macrophages (melanophages, siderophages) and inflammatory cells, mainly lymphocytes. In a few cases, pigmented an nonpigmented epithelial cells of the ciliary body were encountered, retinal sensory cells only in one case. Fibroblasts and fragments of granulation tissue occurred in four of the 14 diabetic cases, in four of the 21 posttraumatic cases, in one case of chronic uveitis as well as in one case of retrolental fibroplasia. Fragments of ciliary body were in three specimens from injured eyes. In one case of chronic uveitis slight suspicion of ciliary body melanoma was aroused on the basis of distinct cellular atypia. There was agreement between clinical and cytological diagnosis in most cases, but particularly in posttraumatic and inflammatory diseases cytologic examination offered new diagnostic data. This is a new method of microscopical verification of the condition in the vitreous body in various diseases. Our experiences are preliminary but we feel that this method has proven its availability.