An improved method has been used for rapid determination of the ionic strength ( I) and the salinity of Apulian groundwaters. The parameters required are the electrolytic conductivity ( EC) and the total solute concentration (C T) of the solutions. A simple empirical relation between I, EC and C T is presented. The relation holds over a wide concentration and composition range. The combined use of C T and of the ratio I/C T is shown to be effective in defining the salinity of groundwaters.