Divalent cations, such as calcium and magnesium, are constantly present in extracellular compartment of most organisms. Modification of extracellular concentrations of divalent ions causes changes in physiologic functions, such as, excitability and conduction of the. nerves. The present study was designed to investigate and compare the effects of calcium and magnesium on nerve conduction and lidocaine-induced nerve conduction block. The aim of our study was to contribute to better understanding of physiological and pharmacological roles of divalent cations.