During the course of a hydrogeological investigation into saline groundwater problems in a Permo-Triassic Sandstone aquifer in northwest England, an opportunity was taken to obtain focused electric logs in 12 fully penetrating coal exploration boreholes. These logs provided data of a type not usually available in a water industry groundwater investigation because of expensive drilling costs. The data have been used to examine highly mineralized groundwaters which are situated near the base of the aquifer. The technique provides information on the conductivity of both fresh and saline groundwaters, the depth at which conductivity increases and the thickness of the diffusion zone. Comparison of focused electric logs produced in mud-filled boreholes with the more usual hydrogeological technique of conductivity logs in open boreholes shows that focused-electric logs more accurately reflect field conditions.