<i>Purpose:</i> To compare the cellularity of vitreous samples obtained from patients with rhegmatogenous retinal detachment complicated by proliferative vitreoretinopathy (PVR) and from patients with uncomplicated rhegmatogenous retinal detachment (RD) to detect possible variations in cellularity over time. <i>Methods:</i> One hundred and twenty-five vitreous specimens collected from patients with RD (n = 41) and PVR (n = 84) were processed through direct paraffin embedding and cytospin. Different cell types were identified by light-microscopy (hematoxylin-eosin and Papanicolaou stain) according to their morphologic features, and a scale of cellular density was established for each cell type. Student’s t test was used to analyze differences in the cellularity of RD versus PVR. A quadratic model was used to identify variations in the density of each cellular type in the PVR group, based on its evolution time. <i>Results:</i> During the first months after surgery, more macrophages and fibroblast-like cells were observed in the PVR group, but at other times no differences were found. <i>Conclusions:</i> There are some differences in vitreous cellularity in PVR specimens when compared with RD. Especially relevant could be the large number of macrophages in earlier stages and their constant presence over time in PVR samples. The cytology of vitreous samples may shed light on the chronology of PVR cell pathobiology.