Apparent molar volumes (V-2,V-phi) have been determined from density measurements for some nucleic acid bases (uracil, cytosine, thymine), and nucleosides (uridine, cytidine and thymidine) in water and in aqueous solutions of (0.10, 0.25, 0.50, 0.75 and 1.00) mol kg 1 guanidine hydrochloride (co-solute) over the temperature range (288.15 to 318.15) K, at atmospheric pressure using vibrating-tube digital densimeter. These data have further been used to calculate apparent molar volumes V-2,phi(o) at infinite dilution and the corresponding apparent molar volumes of transfer Delta V-tr(2,phi)o 2;/at infinite dilution from water to aqueous solutions of guanidine hydrochloride (GnHCl). Apparent molar expansibilities (Eo 2;/), second-order derivative (partial derivative(2) V-2,phi(0) /partial derivative T-2)(p) and volumetric interaction coefficients have also been calculated. Co-sphere overlap model has been used to rationalize the data in terms of molecular interactions (hydrophilic, hydrophobic and ionic interactions). The present data have been compared and discussed for the systems studied with those reported in the presence of other co-solutes. The contributions of -CH2 group to V-2,phi(o) have also been calculated at different temperatures and concentrations of GnHCl. (C) 2014 Elsevier Ltd. All rights reserved.