A more rapid and a versatile synthetic approach for the preparation of polyhedral silsesquioxanes (POSS) by hydrolytic condensation of organosilicon monomers in the presence of a Pt catalyst was studied. The structural properties of POSS molecules were determined by X-ray powder diffraction analysis, yielding a rhombohedral unit cell with a = 11,52796 angstrom and alpha = 94,9754 angstrom for octaaminopropyl-POSS, and a rhombohedral unit cell with a = 11,51421 angstrom, alpha = 96,7214 degrees for octachloropropyl-POSS. The activation energies were found to be 64.8, and 89.1 kJ/mol for octaaminopropyl-POSS and octachloropropyl-POSS, respectively. The products were also characterized by Fourier transform infrared spectroscopy, H-1 and C-13 nuclear magnetic resonance, differential thermal analysis, and thermogravimetric analysis.