Pure, translucent, and highly crystallized barium titanate (BaTiO3) monolithic gels were synthesized via a sol-gel technique at temperatures down to 90 degrees C by using a high-concentration solution of barium alkoxide and titanium alkoxide, The gels consisted of fine particles with an average diameter of similar to 10 nm and showed the X-ray diffraction patterns of a pseudo-cubic BaTiO3 system at room temperature; however, in bulk crystal, the tetragonal structure was more stable. The optical transmission spectra of the polycrystalline gels were similar to those for single-crystalline BaTiO3, From the excitation energy dependence of the absorption-edge structures, the optical-gap energies for the gels were estimated to have values that were similar to 0.1 eV higher than those for the single crystal; these higher optical-gap energies may be attributed to size effects.