An efficient numerical implementation of the integral equation technique (IE) has been developed for the analysis of the electrical characteristics of finite microstrip structures. The technique formulates a volume version of the IE for the finite dielectric objects and a standard surface IE technique for the metallic areas. The system of integral equations formulated is solved with special numerical techniques described in this paper. The input impedances of several microstrip antennas have been computed, showing good agreement with respect measurements. The technique has shown to be accurate, even for complex geometries containing several stacked dielectric layers. The radiation patterns of the structures have also been computed, and measured results from real manufactured hardware confirm that backside radiation and secondary lobes are accurately predicted by the theoretical model. The paper also discuss a suitable excitation model for finite size ground planes and investigates the possibilities for an independent meshing of the metallic areas and the dielectric objects inside a given geometry. The practical value of the approach derived is that microstrip circuits can be designed, minimizing the volume and size of the dielectric substrates.