An alternative approach, based on simple acid-base hydrolytic chemistry, to prepare organic-inorganic composites is reported. In these hybrid materials, NLO-active chromophores such as Disperse Red 19, a pyridinium salt based dye, and 1-amino-4-nitrobenzene are covalently locked into silica networks. The resulting hybrids are soluble and offer ease of processibility in the preparation of good-optical-quality thin films. Network materials that are akin to the traditional sol-gel approach are also prepared from,the monofunctional NLO chromophore DR1 and, as expected, are found to be insoluble. Physical properties of the NLO chromophore-incorporated hybrids can be tailored by changing the molar amounts of chromophores and water, and the type of chromophore. High thermal stability and glass-transition temperatures of these hybrids offer effective electric-field poling at high temperatures and long-term temporal stabilities of the second-harmonic-generation signals at room temperature and at 80 degrees C. The chi((2)) values for the networks were found to be in the range of (1.2-37) x 10(-8) esu.