AbstractIt is shown that the coefficient of coupling between resonators can be derived by a perturbation method using the electromagnetic field distributions of uncoupled resonators. This method can be applied if identical resonators are symmetrically placed. It is found that there is a possibility of completing the calculations in a shorter time than by using the conventional even and odd mode frequencies. Further, since the electric and magnetic couplings can be derived separately, the physical meaning of the coupling becomes clearer. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 89(8): 27–33, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20251