Raman spectra of spinel LixMn2O4 (x = 1.0 and 1.1) were recorded in situ during electrochemical intercalation of lithium ions. We demonstrate that phases and structural modifications in these compounds can be identified using Raman spectroscopy. In stoichiometric LiMn2O4, Raman spectral results indicated that a single-phase reaction is followed by a two-phase reaction and then by another single phase reaction when Lithium is deintercalated from the spinel compound (0.1 < x < 1.0). In nonstoichiometric LixMn2O4 (x = 1.1), Raman spectra clearly identify the presence of the lambda-MnO2 phase in the cathode during charge and discharge. When spinel LiMn2O4 was intercalated with lithium ions, the in situ Raman spectral changes were? consistent with a two-phase reaction between cubic LiMn2O4 and tetragonal Li2Mn2O4.