Abstract: In this paper the simultaneous integro-differential equations of two arbitrary-shaped thin-wire antennas with point-exitation are given. The formulas to determine the input self-and mutual-immittances are derived using the moment method. These formulas can be simplified by means of rational selection of basis functions and weighting functions. The mutual impedances of parallel circular-loops and coplanar dipoles are calculated as examples respectively, which are found to agree with the experimental data.