['To investigate the apoptotic effect of photoexcited titanium dioxide (TiO(2)) nanoparticles in the presence of visible light on human hepatoma cell line (Bel 7402) and to study the underlying mechanism.', 'Cerium-element-doped titanium dioxide nanoparticles were prepared by impregnation method. Bel 7402 human hepatoma cells were cultured in RPMI 1640 medium in a humidified incubator with 50 mL/L CO(2) at 37 centigrade. A 15 W fluorescent lamp with continuous wavelength light was used as light source in the photocatalytic test. Fluorescence morphology and agarose gel eletrophoresis pattern were performed to analyze apoptotic cells.', 'The Ce (IV)-doped TiO(2) nanoparticles displayed their superiority. The adsorption edge shifted to the 400-450 nm region. With visible light illuminated for 10 min, 10 microg/cm(3) Ce (IV)-doped TiO(2) induced micronuclei and significant apoptosis in 4 and 24 h, respectively. Hochest 33258 staining of the fixed cells revealed typical apoptotic structures (apoptotic bodies), agarose gel electrophoresis showed typical DNA ladder pattern in treated cells but not in untreated ones.'] Does nano-cerium-element-doped titanium dioxide induce apoptosis of Bel 7402 human hepatoma cells in the presence of visible light?