Polymeric materials such as polyimides are used in a multitude of microelectronic applications including interlevel dielectrics for insulation. Polyimide films have shown a difference between the through-plane and in-plane refractive index measurements.(1,2,3) This anisotropy in optical properties has been attributed to in-plane orientation of polymer chains and implies anisotropy in electrical properties. Thus, it is necessary to measure the electrical properties in both the in-plane and through-plane directions to accurately design three-dimensional electronic packages. The purpose of this research is to develop an in-situ technique to measure the in-plane permittivity of these spin-coated polymer films. Using capacitance measurements obtained from interdigitated electrodes, through-plane permittivity measurements, and ANSYS finite element analysis software, the in-plane permittivity of a given material can be determined. Several polyimide systems including Du Pont PI-2611 (BPDA-PPD), Du Pont PI-2540 (PMDA-ODA), and Probimide 293 (BTDA-DAPI) from OCG Microelectronics, as well as Cyclotene 3022 (BCB) from Dow Chemical were investigated. Anisotropy in the permittivity was observed in the three polyimide films, but not in the BCB film. Results were compared with predictions using refractive index measurements and a modified form of Maxwell's equation.