Methoxychlor, an organochlorine pesticide, is thought to be an endocrine disrupter that affects Ca^(2+) homeostasis and cell viability in different cell models. This study explored the action of methoxychlor on cytosolic free Ca^(2+) concentrations ([Ca^(2+)] i) and apoptosis in HA59T human hepatoma cells. Fura-2, a Ca^(2+)-sensitive fluorescent dye, was applied to measure [Ca^(2+)] i. Methoxychlor at concentrations of 0.1-1μM caused a [Ca^(2+)] i rise in a concentration-dependent manner. Removal of external Ca^(2+) abolished methoxychlor's effect. Methoxychlor-induced Ca^(2+) influx was confirmed by Mn^(2+)-induced quench of fura-2 fluorescence. Methoxychlor-induced Ca^(2+) entry was inhibited by nifedipine, econazole, SK&F96365, and protein kinase C modulators. Methoxychlor killed cells at concentrations of 10-130μM in a concentration-dependent fashion. Chelating of cytosolic Ca^(2+) with 1, 2-bis (2-aminophenoxy) ethane-N, N, N', N'-tetraacetic acid/AM (BAPTA/AM) did not prevent methoxychlor's cytotoxicity. Methoxychlor (10 and 50μM) induced apoptosis concentration-dependently as determined by using Annexin V/propidium iodide staining. Together, in HA59T cells, methoxychlor induced a [Ca^(2+)] i rise by inducing Ca^(2+) entry via protein kinase C-sensitive Ca^(2+)-permeable channels, without causing Ca^(2+) release from stores. Methoxychlor also induced apoptosis that was independent of [Ca^(2+)] i rises.