Specific heat capacities (c(p)) and apparent molar heat capacities (C-p,C-2,C-phi) of aqueous 4-hydroxyproline have been measured from T = (298.15 to 328.15) K over the molality range of (0.101708 to 2.031524) mol.kg(-1) using micro differential scanning calorimetry. The values of density (rho), apparent molar volume (V-2,V-phi), speed of sound (u), and adiabatic apparent molar compressibility (K-S,K-2,K-phi) have also been determined for aqueous 4-hydroxyproline from T = (288.15 to 313.15) K over the molality range of (0.037934 to 0.786476) mol.kg(-1). The results of these measurements have been used to calculate the following standard partial molar quantities and their temperature derivatives for aqueous 4-hydroxyproline as a function of temperature: C-p,C-2,C-m degrees, (partial derivative C-p,C-2,C-m degrees/partial derivative T)(p), (partial derivative C-2(p,2,m)degrees/partial derivative T-2)(p), V-2,V-m degrees (partial derivative V-2,V-m degrees/partial derivative T)(p), (partial derivative V-2(2,m)degrees/partial derivative T-2)(p), K-S,K-2,K-m degrees, (partial derivative K-S,K-2,K-m degrees/partial derivative T)(p), and (partial derivative K-2(S,2,m)degrees/partial derivative T-2)(p). Isothermal titration calorimetry has been used to determine the heat of dilution (q) of aqueous 4-hydroxyproline and aqueous L-proline in water over the temperature range from (288.15 to 308.15) K. The results have been discussed in terms of the changes in interactions of 4-hydroxyproline and L-proline molecules in the aqueous form, and their water structure promoting ability with rise in temperature. (C) 2009 Elsevier Ltd. All rights reserved.