Measurements of the equivalent conductivity of aqueous solutions of lithium, sodium, potassium, and cesium salts of carboxymethylcellulose (CMC) at 25 °C are reported. The degree of substitution of the CMC used was 0.86, concentrations of the four salts were varied from 5 × 10−4 to 5 × 10−2 equiv l−1. Results show a decrease of Λ with increasing concentration in each case. In the lower concentration range (up to 10−2N) this decrease is in close agreement with a limiting law for conductivity recently developed by Manning. Above 10−2N the decrease in Λ is less than the decrease predicted by the limiting law. The counterion dependence of Λ is accurately predicted by the theory, and a qualitative agreement is obtained when the theory is used to compare conductance data of polyelectrolytes with different charge densities.