The thermal conductivity, λ, of n-dodecane, C12H26, has been investigated. The transient hot-wire method was used to determine λ in the temperature range 190–280 K at a pressure of 30 MPa and at about 273 K at pressures up to 1·0 GPa. For a given temperature and pressure the λ values of solid n-dodecane are higher than those of the two neighbouring oddnumbered n-alkanes, n-undecane, C11H24, and n-tridecane, C13H28. The results are discussed with reference to three different crystal structures of solid n-alkanes.