Pd/SiO 2 nanobeads containing tiny Pd clusters with a diameter of about 2 nm were prepared via a sol-gel process for SiO 2 by using a water-in-oil microemulsion with Pd complexes and subsequent hydrogen reduction by heat treatment. The Pd/SiO 2 nanostructures were employed in Suzuki coupling reactions with various substrates, and they served as good catalysts in these reactions.