We obtain a solution of the Dirac equation in the presence of the electromagnetic field of a complex nucleus by means of coupled-channel partial wave analysis using a new method in which the asymptotic solutions of the coupled radial wave equations include all electromagnetic couplings. A compu er program employing this method is used to determine the importance of dispersion effects in the scattering of 250 MeV electrons from Ca40 and Ca44. We find the dispersion effects to be less than 1% for angles below 90°(i.e., considerably less than experimental error over the range investigated experimentally), thus supporting the view that the difference in the differential cross sections from Ca40 and Ca44 arises primarily from a difference in the ground state charge distributions of the two isotopes. NUCLEAR REACTIONS Ca40(e, e′), Ca44(e, e′), E=250 MeV, E=50 MeV, calculations; coupled-channel calculation of dispersion effects; energy dependence of dispersion effects. © 1977 The American Physical Society.