Cubic mesoporous CdS crystalline nanoparticles (4-6 nm) have been prepared by template-free ultrasonic-mediated precipitation, employing simple inorganic precursors at room temperature. The N2 adsorption-desorption isotherm reveals that the as-prepared CdS nanoparticle has an average pore size of ≈5.4 nm. Copyright © 2007 The Chemical Society of Japan.