A detailed investigation of d.c., a.c. and complex plane polarographic behaviour of copper(I1) inmixtures of monoethanolamine and sodium perchlorate and monoethanolamine and monoethanolanumnium perchlorate is made. In solutions containing monoethanolamine and sodium perchlorate, the reduction is found to be two-electron addition process, the extended d.c. wave being due to more than one complex species in sluggish equilibrium. The a.c. and complex plane polarographic techniques show reduction due to only one of the species. The formula of the species is given on the basis of a.c. sumnit potential shift with change in ligand concentration. In solutions containing monoethanolamine and monoethanolammonium perchlorate, two 1:l waves are obtained in d.c. polarography, the separation increasing with increase in monoethanolammonium perchlorate concentration. Corresponding to the two d.c. polarographic waves, the a.c. and complex plane polarograms also indicate two peaks. On the basis of complex plane polarography, the rate constants of the various processes have been determined. Based on the d.c. polarography, the formulae and stability constants of copper(I1) and copper(1) complexes have been determined. The composition of the two complex species are given as CuM30H+ and CuMf.