Abstract: The invention relates to the measurement of the ovalization of a ferromagnetic pipe.An electromagnetic pickup is moved in a circular path around the pipe, the pickup transmitting signals influenced by the radial distance between the pickup and the pipe. These signals are compared with signals from previous measurements made on a similar pipe to obtain indications of the radial distance between the pickup and the pipe so as to be able to deduce the transverse configuration of the pipe. The pickup is supplied with ac at a frequency of about 700 Hz and the signals from the pickup are compared with previously obtained signals both as to amplitude and phase.The pickup is mounted on a circular slide movable along a circular track supported on a U-shaped collar which is fixed to the pipe.