Recent development for shape selective catalysis by microporous heteropoly compounds has been reviewed. Synthesis and characterization of microporous heteropoly compounds with different cations and compositions have been described first. Pore-size distributions of the heteropoly compounds and their Pt-promoted bifunctional catalysts have been determined by means of adsorption of Ar and N-2. It was revealed that M-2.1 H0.9PW12O40 and 0.5 wt.% Pt-M2.1H0.9PW12O40 (M = Cs, Rb, and K) possessed only ultramicropores, while the pores of Pt-CsxH3-xPW12O40 (x = 2.3, 2.5, 2.8 and 3.0) showed bimodal distributions in the range from micropore to mesopore. From the adsorption of various molecules including n-butane and isobutane, the pore width of Pt-Cs2.1H0.9PW12O40 was determined to be close to the molecular size of n-butane, that is, 0.43 nm. The fraction of external surface area in the total surface area of Pt-Cs2.1H0.9PW12O40 was estimated to only 0.06. The micropore-sizes of Rb2.1H0.9PW12O40 and Pt-Rb2.1H0.9PW12O40 were estimated to be about 0.6nm. Cs2.1H0.9PW12O40 and Pt-Cs2.1H0.9PW12O40 exhibited reactant shape selectivity for acid-catalyzed reaction, and hydrogenation and oxidation of smaller molecules, respectively, due to the uniform ultramicropores and small external surface areas. Furthermore, Pt-Rb2.1H0.9PW12O40 exhibited shape selectivity for hydrogenation of aromatic compounds. (C) 2003 Elsevier B.V. All rights reserved.