The absorption spectra of Lanthanides have been a subject of several investigations1. Recently spectral intensities of Pr3+and Nd3+β-diketonates have been reported2,3by the authors. In Nd3+complexes4I9/2→4G5/2'2G7/2transitions, obeying the selection rule δJ ≤ 2, are known to give rise to intense bands3,4. Since these bands are sensitive to both ligand and solvent, they are known as hypersensitive transitions. The explanation of the phenomenon of hypersensitivity has proved to be an intriguing problem. In the present communication the various theories advanced to explain this phenomenon have been examined in the light of the recent studies of spectral intensities.