ABSTRACT: Time dependent density functional theory (TDDFT) calculations have been carried out to study the electronic structure and the UV absorption spectra of Triamterene. The UV spectra have been investigated with inclusion of solvent effect. The B3LYP functional with a 6-31G(d, p) basis sets have been used to compute absorption energies. The solvent effects have been described within the polarizable continuum model (PCM). The geometries are optimized using density functional theory (DFT) with B3LYP functional combined with 6-31G(d, p) basis sets. The vertical absorption energies both in gas phase and in polar solvents such as ethanol, methanol and water were computed. Red-shift of the absorption maximum in the polar solvents is discussed in terms of electrostatic interaction energy, oscillator strength and dipole moment.