BACKGROUND The control of retinal pigment epithelial cell proliferation is an essential factor in the clinical management of proliferative vitreoretinopathy (PVR). Factors inhibiting PVR without toxic potential are of special interest in ophthalmology. The aim of the study was to investigate the antiproliferative and cytotoxic effects of a preservative-free triamcinolone acetonide (PFTA) suspension on a human retinal pigment epithelial (ARPE19) cell line in vitro. METHODS ARPE19 cells (immortal non-transformed cells from a human donor) were seeded and incubated in vitro with increasing concentrations of PFTA (0.01-1 mg/ml). After 1, 3, and 7 days, cellular proliferative activity was assessed by 5'-bromo-2'-deoxyuridine (BrdU) incorporation into cellular DNA and cell proliferation was determined using the 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assay. To determine cytotoxicity, ARPE19 cells were grown to confluence and subsequently cultured in serum-deficient medium to ensure a static milieu and the MTT test was performed after 24 hours of incubation with PFTA. Cell recovery after transient PFTA exposure was also compared with continuous exposure after 7 days. RESULTS PFTA inhibits ARPE19 cell proliferation in a dose-dependent manner. Significant inhibition of cell proliferation was observed on the first day of the study at 1, 0.1, and 0.01 mg/ml PFTA and significant reductions in ARPE19 cells were noted for 1 and 0.1 mg/ml PFTA. Proliferation was resumed in all ARPE19 cultures and was dependent on the initial PFTA concentration. PFTA did not cause a cytotoxic effect. CONCLUSIONS PFTA influences the proliferation of vital ARPE19 cells in a reversible manner without cytotoxic effect.