We investigated the influence of glycated low density lipoprotein (LDL) for vascular smooth muscle cell (SMC) proliferation or injury. We utilized glycated, slightly oxidized LDL (GLDL-LOX), glycated, auto-oxidized LDL (GLDL) and glycated, metal-induced extensively oxidized LDL (GLDL-OX) to examine the effect of glycation itself or combined glycation and oxidation on SMC. GLDL-LOX induced SMC proliferation and migration, and increased the number of platelet-derived growth factor receptor, β subunits, (PDGF-R) positive SMC. Also, GLDL-LOX promoted protease activity, compared with the other groups including native LDL (control). GLDL and GLDL-OX demonstrated SMC injury with apoptosis and Bax protein expression, compared with native LDL and GLDL-LOX. These results suggested that LDL glycation contributed to the progression of atherosclerosis by promoting SMC migration and proliferation, with little dependence on oxidative modification. Secondary auto-oxidation adding to glycation induced SMC apoptosis, and SMC injury occurred in the state of strong oxidation with glycation. We concluded that LDL glycation might play a key role in the progression of atherosclerosis in diabetes, and glycated LDL promoted atherosclerosis, even with little assistance from oxidation.