Layered calcium organosilicate hybrids contg. covalently linked org. functionalities were synthesized by a sol-gel process from the reaction of calcium salt and organotrialkoxysilane with alkyl (from Me to octadecyl) and Ph functionalities in an aq./EtOH basic soln. at room temp. These hybrid org.-inorg. materials were characterized by XRD, TEM, FTIR, and solid state 29Si, 1H, and 13C NMR spectroscopy. The comparison of the basal distance measured by XRD and the length of the alkyl groups is consistent with a bilayer arrangement of the org. group inside the interlayer. The degree of basal ordering does not depend on the alkyl group length. Broad in-plane diffraction peaks are best explained by a smectite-like layer than by the parent inorg. calcium silicate hydrate (C-S-H) structure. This suggests the existence of edge-sharing Ca(O,OH)6 layers sepd. by well-organized organosilicates. FTIR, 13C, and 29Si NMR spectra exhibit the typical features of Si-C bonds, showing that the org. groups were not cleaved. Also, the 29Si NMR spectrum shows that silanes are fully hydrolyzed but weakly condensated. To the authors' knowledge, this is the first report of the synthesis and characterization of layered calcium silicate with org. functionalities directly bonded to the inorg. framework via Si-C bonds.