Department of Chemistry, Gandhigram Rural University, Gandhigram-624 302, Tamilnadu, India E-mail : drkpelango@rediffmail.com Manuscript received 6 March 2007, revised 17 January 2008, accepted 21 January 2008 Charge-transfer (CT) complexes of ofloxacin, chloropheniramine, azacyclonol and indapamide drugs with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) were investigated spectrophotometrically in different organic solvents at different temperatures. The spectral characteristics and formation constants of the formed 1 : 1 CT-complexes were examined and discussed in terms of the solvent properties. The oscillator and transition dipole strengths of the complexes have been determined from the CT absorption spectra. The ΔH0, ΔS0 and ΔG0 values are all negative, indicating stability and exothermic character of the complexes. The ionization potential value of the donors calculated using spectral data are in good agreement with those computed using molecular orbital package MOPAC (PM3) method. Infrared analysis of the CT -complexes have also been carried out.