A lattice theory, based on a quasi-chemical approach, has been combined with a semimacroscopical theory to calculate the permittivity of water. At low field strength the magnitude and the temperature dependency of the calculated permittivity agree with experimental data. The high-field dielectric behavior of water has also been studied. If the field strength increases, the permittivity goes through a maximum, which has not been found experimentally. This maximum is caused by the fact that orientation of dipoles in the field is strongly cooperative due to hydrogen bonding.