Abstract: Objective: To observe the inhibitory effect of all-trans retinoic acid (ATRA) on the growth of rat C6 glioma cells and to explore the underlying molecular mechanisms. Methods: MTT assay was employed to detect the growth of rat C6 glioma cells treated with ATRA and the inhibition rate was evaluated. Flow cytometry was used to determine the cell cycle distribution and the rate of apoptosis. The ultramicroscopic structure of C6 cells was observed through transmission electron microscopy. Western blot was performed to analyze the expression of caspase-3 proteins in the treated and untreated rat C6 glioma cells. Results: MTT assay results showed that the inhibitory effect of ATRA on the growth of rat C6 glioma cells was dose-dependent and time-dependent. According to the flow cytometry analysis, C6 cells were arrested in G1 phase. The proportion of cells in S and G2 phase was decreased. A typical subdiploid peak was detected in DNA frequency distribution histograms. Signs of apoptosis-like condensation of nuclei and margination of nuclear chromatin were observed at 72 hours after the cells were treated with ATRA. Western blot indicated that rat C6 glioma cells treated with ATRA presented with increased expression of caspase -3 active proteins. Conclusion: ATRA inhibits the growth of rat C6 glioma cells, and its molecular mechanism may involve its induction of changes in cell cycle distribution and apoptosis.