Department of Chemistry, Dr. H. S. Gour University, Sagar-470 003, India E-mail: rashmitiwari@epatra.com Manuscript received 24 July 2001. revised 17 May 2002, accepted 27 August 2002 Electronic spectral studies of PrIII, NeIII and ErIII in complexation with catechol (cat) have been undertaken with a view to evaluate the oscillator strengths (ƒIO), Judd-Ofelt parameters (\( {\displaystyle \tau \,}\)\(\lambda \,\)), inter-electronic repulsion Racah parameters (δEK) and nephelauxetic ratios (δE3/δE1) in the pH range 4.0-6.0. The extent of covalency in metal-ligand interaction have been estimated. The oscillator strength values for some specific hypersensitive transistions were found to be significantly large.