Experimental values of the thermal conductivity λ and thermal diffusivity a of 29 pure substances are presented in the temperature range of -15 °C to 65 °C under atmospheric or saturation pressure. The materials measured were as follows: alkenes (1-pentene, 1-hexene, 1-heptene, 1-octene, 2,3-dimethyl-1-butene, 2,3-dimethyl-2-butene), cycloalkenes (cyclopentene, cyclohexene), cycloalkanes (cyclopentane, cyclohexane, methylcyclopentane, cycloheptane, cyclooctane), aromatics and their relatives (benzene, ethylbenzene, o-, m-, and p-xylenes, propylbenzene, isopropylbenzene, hemimellitene, pseudocumene, mesitylene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, bicyclo[2.2.1]hepta-2,5-diene [norbornadiene]), and deuterated hydrocarbons (benzene-d 6 , cyclohexane-d 12 , toluene-d 8 ). Measurements were made with the transient hot-wire method in the manner previously presented, and the thermal diffusivity values were corrected by reference to the heat capacity of heptane as a reference material. Heat capacities (volumic, c p F; massic, c p ; molar, C m,p ) were complementally derived from the relationship c p F ) λ/a, with values for the density and the molar mass. The uncertainty of the data is estimated to be 0.4% for the thermal conductivity (absolutely measured) and about 1.8% for the thermal diffusivity (with a coverage factor of k p ) 2; p ) 95%), although that of λ (not of a) is possibly inferior for a few substances containing slightly more impurities (i.e., mainly other isomers).