Indapamide blocks multiple voltage-dependent K + currents (K v ) in the heart and K v have an important role in cell proliferation and apoptosis, so the aim of this work was to study the effects of indapamide on K v and the viability of GH3 cells. Indapamide inhibited K v of GH3 cells and the inhibition was irreversible after a 10-min washout when more than 250 μM indapamide was used. Indapamide reduced the viability of GH3 cells in a concentration-dependent manner. The decreased cell viability was because indapamide induced cell apoptosis, or even necrosis at higher concentrations. HepG2 cells, which express no apparent K v , were used to determine the association between inhibition of K v and the apoptotic action of indapamide. Indapamide had a similar action on cell viability and apoptosis of HepG2 cells. 4-Aminopyridine, the voltage-dependent K + channel blocker, inhibited K v of GH3 cells but did not induce the cell apoptosis. We concluded that while indapamide inhibited K v and induced apoptosis of GH3 cells, the apoptotic action of indapamide was not associated with its inhibition of K v .