Pentoxifylline is used to improve blood flows through peripheral blood vessels. The density of three amino acids and two peptides (glycine, L-alanine, L-valine, glycylglycine, and glycylglycylglycine) are measured using DSA 5000 instrument at T = (293.15, 298.15, 303.15, and 308.15) K in aqueous solution of this compound. The apparent molar volume, (V-phi), partial molar volume, (V-phi(0)), transfer partial molar volume, (Delta V-phi(0)), and partial molar expansibility, (E-2(0)), thermal expansion coefficient, (alpha(2)), and Hepler's constant, (partial derivative V-2(phi)0/partial derivative T)(2) are calculated from the density data. The above parameters are used to interpret the solute-solute and solute-solvent interactions of amino acids/peptides in aqueous pentoxifylline solution. The dependence of these parameters upon concentration and temperature clearly suggest the role of amino acids/peptides and pentoxifylline in solute-solvent interactions. (C) 2012 Elsevier Ltd. All rights reserved.