A modified protocol for quick and economic treatment of cultured human umbilical vein endothelial cells has been established, which result in high viability of the cells to allow better performance in patch-clamp studies. The electrophysiological properties of Ca (2+)-activated K(+) (KCa) channel of the cultured cells were investigated with a cell-attached configuration. With this modified treatment method, the cultured cells appear fusiform in shape under microscope, and KCa channel currents could be detected readily, suggesting their eligibility for patch-clamp studies.