DNA profiling studies revealed that STR patterns of the endothelial line ECV-304 and the human bladder line T24 were very similar, suggesting that ECV-304 was a derivative of T24. Furthermore, ATCC karyotypes of the two lines show two shared-marker chromosomes. Combined, these results show that ECV-304 is indeed a derivative of T24, a line that was developed years earlier. It is important to emphasize that all stocks of ECV show similar properties.