A modification of the Falkenhagen equation is proposed, which fits correctly data of 29 different 1:1 aqueous electrolyte solutions up to very high concentrations. The concept of activity is used to account for deviations from ideality appearing at higher concentrations. A discussion about trends in the value of the ＇distance of closest approach between two ions＇, a, and novel conductivity data for several concentrated electrolyte solutions estimated by the proposed model are also provided.