Previous investigations on the variation with frequency of the initial inner permeability &mgr;Lof iron reveals great disparity of results. In this experiment certain refinements of technique and of analysis have been introduced which make the accuracy adequate for comparison with theory. The method used was to determine the change in resonant frequency of a coil and condenser combination caused by insertion of a permeable sample in the field of the coil. This change in frequency is interpreted as being caused by change of flux through the coil. The same iron wire had been measured previously over a different frequency range by other men working in this laboratory. The value of &mgr;Lwas found to be ∼60 over the frequency range from 30 kc to 40 mc showing no dispersion region between these limits. Results of this method are compared with those of other methods.