The interactions between prostate cancer cells with endothelial cells in the microvessels play an important role in prostate tumor metastasis. However, not many studies have been conducted to investigate the adhesion of prostate cancer cells on vascular endothelium and related mechanisms and modulators. In this study, human microvascular endothelial cells (HMEC) grown on glass slides were exposed to two different circulating prostate cancer cells, PC-3 and PC-3ML (highly metastasis prostate cancer cells) using an in vitro parallel flow system. The gene profiles of HMEC, after exposure to prostate cancer cells, were also investigated using cDNA microarrays. It was found that PC-3ML cells had significantly higher adhesion than PC-3 cells on HMEC monolayer. In addition, PC-3ML cells triggered more gene changes of HMEC than PC-3 cells did. These results suggested that prostate cancer cells might increase their adhesion to vascular endothelial cells by affecting the endothelial cell on the gene expression level.