Aim To determine the expression of human tissue-type plasminogen activator (tPA) cDNA in mamalian cells. Methods A recombinant retroviral vector containing tPA gene was constructed and transtected into bovine endothelial cells (EC) by retroviral vector-mediated gene transfer. The tPA activity of transduced cells was measared with casein-plastninogen-agarose plate and a synthetic-peptide substract S-2390.Results The viral titer was 4 ×108 cfu/L. Trans-fection effciency was 6×108 colonies/g DNA/106 cells. The tPA activity of transduced cells was obvi-ously increased. Immunohistochemistry analyses confirmed the expression of tPA gene in the genetically engineered cells.Conclusions Retroviral vector mediated gene trans-fer can be used to enhance the fibrinolytic activity of EC. It might be an approach for tPA gene therapy.