Aim To understand the monocyte chemoattractantprotein-1 (MCP-1 ) expression by the cells in dietaryatherosclerotic lesions in rabbits. .Methods The male 4～6 week old Japanese 1p rab-bits were fed on cholesterol to develop a hyperlipidemiaand atherosclerosis model. The MCP-1 mRNA ex-pression in the plaques was examined by dot blot anal-ysis using a probe of P-end-labeled 35-mer oligonu-cleotide of MCP-1. Meanwhile, the MCP-1 in themedia conditioned by cultured SMCs from theatherosclerotic lesions was determined by using sand-wich ELISA. Immunohistochemically, the expres-sion of MCP-1 in various cells in the plaques was ex-amined using a rabbit anti-MCP-1 polyclonal antibody,and to recognize the cells in the plaques, several anti-bodies including factor Ⅶ related antigen, a1-antit-rypsin and a-smooth muscle actin were used.Results Dot blot analysis showed that after hybridiza-tion of the RNA with the probe, the integral opticaldensity value (4. 1 5 ) of the autoradiographic pictures ofthe dots from the atherosclerotic lesions was 10. 7times the controls(0. 38). The MCP-1 content in themedia conditioned by cultured SMCs from theatherosclerotic lesions , asthe ELISA showed,was significantly higher than thatof the normal SMC conditioned media (7. 0±0. 7 g/L) and unconditioned medium (6.4 ±0. 7 g/L) (P<0. 01 ). Immunohistochemically, endothelial cells,macrophage derived foam cells and SMCs in theplaques were positively stained with anti-MCP-1 anti-body in varying degrees. Of the three cell types, themacrophage derived foam cells showed the strongestimmunostaining.Conclusion Under hyperlipidemic condition, theartery wall cells which participate in the developmentof atherosclerotic plaques were in full activity, andproduced and secreted MCP-1 in different degrees.The production of MCP-1 mainly by macrophages sug-gests that they play an important role in the recruit-ment of additional monocytes to the atheroscleroticplaques.