TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractTwo field test examples of formation resistivity logs acquired through metal casing are presented. There is good agreement between the acquired logs and the open hole resistivity logs measured prior to the completion of the wells. The casing collar effects are successfully compensated by the measurement scheme. Error propagation analysis shows that through casing resistivity measurements can have better accuracy of water saturation estimation than provided by pulsed neutron tools for low porosity formations. A comprehensive review of the history of the technology is presented.