Several insertion mutants of Escherichia coli in the ant gene, coding for $Na^{+}$ $H^{+}$ antiport activity, showed littel, if any, reduction in the antiport activity. $Na^{+}$ dependent transport activity also remained at wild type level. These facts led to the idea that E. coli has evolved at least two distinct systems for extrusion of $Na^{+}$ The antiport activities were studied under various conditions to reveal different properties of these systems. For convenience these activities are referred to as major and minor activities. The distinguishing properties of the two systems include : kinetics (Km, Vm) at pH 7.8, competition pattern between $Na^{+}$ and Li$^{+}$ , pH profiles, pattern of the change in kinetic parameters as a function of pH, and sensitivity to protease, chemicals and heat.