Aggregation states and electro-optical effects based on light scattering have been investigated for polymer (liquid crystal) composite films. The composite film was prepared by a solvent- evaporation method. Since a continuous liquid crystalline domain is embedded in a three-dimensional spongy network of polymer matrix, the liquid crystalline material is self-supported in the composite film in spite of its very low viscosity. The composite film composed of poly(methyl methacrylate) and a nematic LC(E44) with positive dielectric-anisotropy exhibited remarkable and reversible light scattering-light transmission switching under the modulation of an ac electric field. A light scattering state was dependent on optical heterogeneities such as a spatial distribution of nematic directors and/or mismatching in refractive indices of the components. Reversible and bistable electro-optical effects were also recognized for a smectic phase of a binary composite system composed of liquid crystalline polymer (LCP) and nematic LC. A light-addressed optical information storage of the LCP/nematic LC/(photoresponsive molecule) ternary composite membrane has also been demonstrated.