Isobaric molar heat capacities at atmospheric pressure were determined for the ternary system dimethyl carbonate + p-xylene + n-decane and the corresponding binary mixtures dimethyl carbonate + p-xylene, dimethyl carbonate + n-decane and p-xylene + n-decane over the whole composition range at 288.15, 298.15 and 308.15 K. From these data, excess isobaric molar heat capacities were calculated using the Benson and Kiyohara's criterion. The obtained values for the binary systems were correlated using a Redlich-Kister polynomial, whereas the ternary contribution was fitted by means of the Nagata equation. The data present a gradual crossover from a W-shaped composition dependence, typical in alkyl carbonate + alkane systems, to negative parabolic curves, often found for alkyl carbonate + aromatic hydrocarbon and for aromatic + linear hydrocarbon systems. The results are discussed in terms of the degree of randomness of the mixtures. (c) 2005 Elsevier B.V. All rights reserved.