Rogowski current probes are used for contact free measurement of non-stationary or transient very high currents. Most often a Rogowski probe must be specially designed for the particular measurement situation at hand. This includes the selection of sensitivity and frequency bandwidth. However careful the probe design is undertaken the probe still has to be calibrated against a known current. This report describes the basic theory of Rogowski probes, some practical design considerations and gives as examples two probes designed for current measurement at different places in a laboratory high voltage generating equipment used. An equipment constructed for calibration of fast probes is also described. The report constitutes a partial documentation of the measurement technology used in experiments conducted within the FOI research project on HPM weapons technology. The purpose of the report is to give a fundamental understanding of the Rogowski probe concept, document our design and constitute a basis for the construction of new Rogowski probes, adapted to measurement situations with differing demands.