Aim To examine whether procucol could inhibit vascular smooth muscle cells(VSMC) proliferation by impairing cell cycle progression. Methods Initially,quiescent rat VSMC were treated with probucol in the presence of oxidized low density lipoprotein(ox-LDL).Then cell proliferation was measured by MTT assay and cell counts,and cell cycle distribution was analyzed by Flow-cytometry(FCM).Finally,protein expression was examined by western blot. Results MTT assay and cell counts revealed that 25 mg/L,50 mg/L and 100 mg/L ox-LDL stimulated VSMC proliferation in a dose dependent manner.Probucol significantly inhibited VSMC proliferation induced by ox-LDL in a dose and time dependent manner.FCM analysis showed that probucol increased cells in G₀/G₁ by 28.6%(p<0.01,n=3),reduced the cells in S by 83.5%(p<0.01,n=3).Also,100 mg/L oxLDL induced cyclin D1 expression,with peak in 6～12 h.Probucol markedly inhibited cyclin D1 expression by 26% at 6 h and 23% at 12 h respectively(both p<0.01,n=3). Conlusions Probucol significantly inhibits ox-LDL induced VSMC proliferation.This antiproliferative effect of probucol is correlated with suppression of cell progression by blocking the cell cycle in G₀/G₁.Furthermore,suppression of cell cycle progression is associated with the down-expression of cyclin D_1 protein by probucol