Aim To examine the effect of oxidized lipoprotein(a) on the proliferation of macrophages. Methods Murine peritoneal macrophages were cultured in vitro with 2.5～40 mg/L native lipoprotein(a), oxidized lipoprotein(a) or MDA-modified lipoprotein(a), and cells proliferation was evaluated by cell counting and MTT assay. Results When macrophages were incubated with 40 mg/L oxidized lipoprotein(a), cell numbers were increased about 1.5-fold compared with control group, while the growth of these cells was not stimulated by native lipoprotein(a) or MDA-modified lipoprotein(a). Conclusion Oxidized lipoprotein(a) might enhance the progression of atherosclerosis by promoting macrophages proliferation.