A general one-pot solvothermal process was explored to prepare BiOX (X = Cl, Br, I) powders by employing ethylene glycol as the solvent. The as-prepared BiOX powders were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, and nitrogen sorption. The resulting BiOX samples were phase-pure and of hierarchical microspheres consisting of nanoplates. The band gaps of the as-prepared powders were estimated to about 3.22, 2.64, and 1.77 eV for BiOCl, BiOBr, and BiOI, respectively. On the basis of characterization results, we proposed a possible process for the growth of hierarchical BiOX nanoplate microspheres. Moreover, we evaluated their photocatalytic activities on the degradation of methyl orange and compared them with TiO<inf>2</inf> (Degussa, P25) under UV-vis light irradiation and C-doped TiO<inf>2</inf> under visible light (λ>420 nm) irradiation, respectively. It was found that all the BiOX samples were photocatalytically active and BiOI exhibited excellent activity under both UV-vis and visible light irradiation. The resulting hierarchical BiOX nanoplate microspheres are very promising photocatalysts for degrading organic pollutants and other applications. ©2008 American Chemical Society.