X-band electron paramagnetic resonance (EPR) studies of Cr3+ doped lithium potassium sulphate single crystals have been done at room temperature. The Cr3+ crystal field and spin Hamiltonian parameters have been evaluated by employing resonance line positions observed in the EPR spectra for different orientations of external magnetic field. The evaluated g, D and E values are: g(x) = 2.0763 +/- 0.0002, g(y) = 1.9878 +/- 0.0002, g(z) = 1.8685 +/- 0.0002 and D = 549 +/- 2 +/-10(-4) cm(-1), E = 183 +/- 2 x 10(-4) cm(-1). Using EPR data the site symmetry of Cr3+ ion in the crystal is discussed. Cr3+ ion enters the lattice substitutionally replacing K+ site. The optical absorption study of the single crystal is also done in 195-925 nm wavelength range at room temperature. By correlating optical and EPR data the nature of bonding in the crystal is discussed. The calculated values of Racah parameters (B and C), crystal field parameter (D-q) and rephelauxetic parameters (h and k) are obtained as: B = 697, C = 3247, D-q = 2050 cm(-1), h = 1.146 and k = 0.21. (C) 2009 Elsevier B.V. All rights reserved.