To clarify the hemolytic mechanism of Bis-GMA and its related methacrylates, the interaction of five methacrylates (Bis-GMA, MMA, NPGDMA, TEGDMA, and UDMA) with DPPC/Cholesterol (CS) liposomes, as a model for erythrocyte membranes, was studied by ¹H-NMR spectroscopy. Exogenous Bis-GMA partitioning into the DPPC/CS liposomes caused disappearances of its proton signals. With NPGDMA, its signals broadened markedly in DPPC/CS liposomes. UDMA partitioning caused changes in chemical shifts to a higher field, whereas MMA and TEGDMA partitioning did not cause any changes in chemical shifts. It was concluded from these observations that Bis-GMA has a stronger interaction with the DPPC/CS liposomes than the other methacrylates used. The high hemolytic activity of Bis-GMA reported previously^{3, 12)} seemed to be due to its migration into the lipid bilayer of phospholipids containing CS in erythrocyte membranes.