TSEC are an SV40-immortalized cell line, derived from hepatic sinusoidal endothelial cells (HSEC), that maintain an endothelial phenotype as well as some HSEC-specific features. The cells have typical microscopic features of endothelia, including formation of lamellipodia and filopodia and a cobblestone morphology of cell monolayers. TSEC maintain a limited number of fenestrae organized in sieve plates and express endothelia-specific markers. TSECs migrate in response to angiogenic factors, form vascular tubes, perform endocytosis, and remodel extracellular matrix. Their phenotype most closely resembles the pathological neovasculature associated with chronic liver disease. Importantly, the cells can be transduced efficiently with viral vectors. TSECs should provide a reproducible cell culture model for high-throughput in vitro studies pertaining to a broad range of liver endothelial cell functions.