In continuation of our studies on the complexes of lanthanide(III) ions with N-donor ligands1,2, especially those of 1,10-phenanthroline (phen)3,4, we wish to report the proton N.M.R. spectra of several lanthanide(III) complexes of phen in aqueous (D2O) solution at 330 K. Table 1 contains the observed chemical shifts of the four types of protons in phen relative to the methyl resonance of the internal standard 2-methyl-2-propanol. For comparison, the spectrum of an authentic sample of Nd(phen)2Cl3.2H2O complex prepared by the method of Sinha5was recorded and the spectrum found to be virtually indistinguishable from that obtained by mixing the individual components in the proper ratio.