Abstract: The invention disclosed comprises a method of and apparatus for inspecting a pipeline in situ. An alternating voltage is impressed between the pipeline and a ground bed. Spaced electrodes are positioned transverse the pipeline at spaced locations along the pipeline. At each location, the current flowing between the electrodes is used to indicate the condition of the coating on the pipeline. In one aspect of the invention, the current flowing between electrodes is obtained by measuring the resistance of the medium in which the pipeline is buried, such as the ground, and the voltage, and then dividing the voltage by the resistance. In another aspect of the invention, the ratio of the resistive and reactive components of the current flowing between the pipeline and the ground bed is used to indicate the quality of the pipeline coating. In yet another aspect of the invention, the third harmonic content of the voltage is measured to obtain an indication of the presence of iron oxide.