An implantable electric field probe with an interference-free lead wire system was constructed at a nominal cost for the purpose of measuring the induced electric fields in a phantom model of man irradiated by waves of various frequencies. The probe consisted of a short dipole loaded with a zero-bias microwave diode, and the interference-free lead wires were constructed with two series of lumped resistors of 3 k Ω. Characteristics of the probe were checked first by measuring the induced electric fields in irradiated, electrically small cubes filled with phantom material. The measured results were in good agreement with theoretical results obtained from the tensor integral equation method. A phantom model of man was constructed with thin Plexiglas filled with phantom material. The model was irradiated by 500- to 3000-MHz em waves in a microwave anechoic chamber. Induced electric fields were probed over 28 locations in one side of the model. The distribution of the measured electric fields was compared with the distribution of theoretical results obtained numerically from the tensor integral equation methods. A qualitative agreement was obtained between experiment and theory. It was found that the agreement between experiment and theory tended to deteriorate at lower frequencies. The reason for this discrepancy is explained.