Mesoscopic organosilicas were synthesized with bis(triethoxysilyl)ethane (BTSE) and cetyltrimethylammonium chloride (CTAC) under basic conditions. Further functionalization was achieved by co-condensation with trialkoxyorganosilanes. Surfactant extraction produced periodic mesoporous organosilicas (PMO's) functionalized with the respective organosilane pendent groups. Organosilanes used in this study include: 3-amino-propyltrimethoxysilane, n-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 2-(trimethoxysilylethyl)pyridine, n-(3-triethoxysilylpropyl)-4,5-dihydroimidazole, phenethyltrimethoxysilane, and benzyltriethoxysilane. These materials have been characterized by nitrogen gas adsorption, powder X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), elemental analysis (EA), and high-resolution thermogravimetric analysis (TGA). The effect of organosilane incorporation on the porous structure of these materials is examined.