In this study, electronic and nonlinear optical properties of six phenyltriazine isomers were calculated. The calculated properties are electronic energy, HOMO-LUMO energies, static polarizability alpha, anisotropy of polarizability Delta alpha, and first static hyperpolarizability beta at equilibrium geometry and their torsional dependence. The torsional barriers and potential energy curves were calculated at HF/6-31++G(d,p) and B3LYP/6-31++G(d,p) methods. The number of ortho hydrogen atoms mainly determines the torsional barriers of these molecules, while the meta hydrogen atoms have a small influence on the equilibrium torsional angles and barriers. Nonlinear optical properties (NLO)-dihedral angle theta correlations of phenyltriazine isomers were calculated at the B3LYP/6-31++(d,p) level. Polarizabilities of phenyltriazines decrease with shifting the nitrogen atoms to the para position. On the contrary, hyperpolarizabilities of phenyltriazines increase with shifting the nitrogen atoms to the ortho position. (C) 2006 Elsevier B.V. All rights reserved.