Retinal pigment epithelial (RPE) cells, which proliferate and dedifferentiate under several pathological conditions, and cultured RPE cells have been considered a good model for comparison. In this investigation, we compared the properties of RPE cells in proliferative vitreoretinopathy with that of cultured human RPE cells. mRNAs of RPE cells from patients with proliferative vitreoretinopathy and from cultured human RPE cells were extracted, and reverse transcriptase-polymerase chain reaction was performed. We also examined cells that were aspirated from bare RPE surface from a patient with a giant retinal tear. We amplified the interleukin-6 gene in the proliferative membranes and cultured RPE cells. We also amplified the tyrosinase gene in seven of eight proliferative membranes, as well as tyrosinase-related proteins and cellular retinaldehyde-binding protein genes, but not the tyrosinase gene in cultured RPE cells. The cells aspirated from bare RPE surface showed reduced activity for expressing interleukin-6 and tyrosinase genes. The dedifferentiation characteristics of cultured RPE cells were different, in that they were less active than RPE cells in proliferative membranes for expressing the genes of melanogenesis, which are essential for pigment cells. Interleukin-6 and genes that were related to melanogenesis were expressed in the proliferative membranes and may play an important role in the generation of proliferative vitreoretinopathy.