The arterial smooth muscle cells (SMC) are the predominant type of cells in atherosclerotic lesions, and their proliferation plays an important role in the process of AS genesis. We established the primary culture and sub-culture method for human arterial SMC and observed the effects of LDL, VLDL, HDL, OX-LDL, OX-VLDL and OX-HDL on the morphological appearance and phenotype of cultured human arterial SMC. The results revealed that the cells cultured in the medium containing OX-LDL, OX-VLDL and OX-HDL (25 micrograms/ml) became more irregular with long finger-like projects and lacked a bipolar shape, and the characteristic "hills" and "valleys" disappeared. LDL and VLDL also had the influence but in smaller degrees. HDL did not have any effect. The SMC cultured in the presence of OX-LDL (25 micrograms/ml) had less myofilaments and more endoplasmic reticulua, Golgi and mitochondria in cytoplasm compared with the cells in control group under electronmicroscope. These results suggest that the atherogenic role of LDL, VLDL, OX-LDL, OX-HDL, and OX-VLDL are closely related to their stimulating effects on the modulation of phenotype of arterial SMCs from "contractile" towards "synthetic".