In order to study the effect of and mechanism of lysophosphatidylcholine (LysoPC) on proliferation of the calf thoracic aorta smooth muscle cells (ASMCs), the ASMCs were used to observe the effects of LysoPC induced endothelial cell conditioned medium on the DNA content and proliferating cell nuclear antigen (PCNA) expression in the calf thoracic ASMCs by flow cytometry and Western Blot technique. It was found that LysoPC induced endothelial cell conditioned medium could significantly promote PCNA expression of the calf ASMCs, induce the converting of ASMCs from G 0 /G 1 phase to S phase of DNA synthesis, and increase the tyrosine phosphorylation protein expression. Tyrosine protein kinase inhibitor (TPKi) RG50864 could obviously inhibit proliferation of LysoPC induced ASMCs in a dose dependence manner. The results indicated that the effect of LysoPC promoting the proliferation of ASMCs is partly evoked by endothelial cell derived growth factors such as PDGF and so on. In order to study the effect of and mechanism of lysophosphatidylcholine (LysoPC) on proliferation of the calf thoracic aorta smooth muscle cells (ASMCs), the ASMCs were used to observe the effects of LysoPC induced endothelial cell conditioned medium on the DNA content and proliferating cell Nuclear antigen (PCNA) expression in the calf thoracic ASMCs by flow cytometry and Western Blot technique. It was found that LysoPC induced endothelial cell-mediated medium could significantly promote PCNA expression of the calf ASMCs, induce the converting of ASMCs from G 0 / G 1 phase to S phase of DNA synthesis, and increase the tyrosine phosphorylation protein expression. Tyrosine protein kinase inhibitor (TPKi) RG50864 could obviously inhibit proliferation of LysoPC induced ASMCs in a dose dependent manner. The results indicated that the effect of LysoPC promoting the proliferation of ASMCs are partly evoked by endothelial cell derived growth factors such as PDGF and so on.