The complexation between Pb(II) and tartrate has been used to experimentally ascertain the effect of precision in the ΔE1/2measurement and ligand concentration range upon the data analysis of the polarographic method of studying metal complex equilibria. The need to obtain data at the lowest ligand concentration possible and with ΔE1/2≤ 0.4–0.6 mV was clearly shown. If this precision is unachievable, data from some other technique, based upon a different property, may be required. These experimental results are in agreement with the simulation study of Klatt and Rouseff (Anal. Chem.,42, 1234 (1970)).