Calculations have been performed on models of Langmuir‐Blodgett LB films to explore how molecular nonlinear response expresses itself in film response. The molecules are treated as a string ofsbeads initially arranged normal to the film with their long axes forming a close‐packed hexagonal array, but they are then allowed to tilt away from the vertical. The molecular polarizability &agr; and first hyperpolarizability &bgr; are represented by one‐dimensional models in which the axial components arestimes the perpendicular ones. Because of the layer structure of the films, the dipolar interactions are calculated as planewise sums between one molecule and all the molecules in a given layer. The sums have been calculated for various values ofsas a function of tilt; they are negligible except for interactions of a molecule with its own layer. They have been used to calculate the local electric field, refractive index and quadratic susceptibility &khgr;(2)for thin films. The results show that tilt has a major effect on the pattern of components of &khgr;(2)and hence on measured nonlinear optical behavior. Such information can be used to help guide the design of molecules to achieve desired film properties.