We report local electric field calculations in nanocomposite materials. These calculations are performed by means of a recursive transfer matrix method initially developed for calculating the electromagnetic field response for three-dimensional systems of scattering spheres. Illustrative calculations are presented for various morphologies of nanocomposites composed of gold particles in a silica matrix. We particularly point out that mutual interactions between particles are responsible for large local field enhancements as compared with fields inside isolated particles. Nonlinear optical measurements, performed by using the z-scan technique, are presented afterwards. We especially study the variations of the imaginary part of the third-order nonlinear susceptibility as a function of the metal concentration and we show that these results are in agreement with the previous field calculations