The paper is aimed at a thermodynamic description of linear siloxanes by a molecular based equation of state. First, experimental data of the five linear siloxanes hexamethyidisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, dodecamethylpentasiloxane, and tetradecamethylhexasiloxane are compiled. As data at higher temperatures are scarce, it is helpful to extrapolate vapour pressures and saturated liquid densities by appropriate equations using the critical temperatures and pressures. The three parameters of the molecular based PC-SAFT equation of state can be fitted either directly to the experimental vapour pressures and saturated liquid densities or to the extrapolation equations. Comparisons of thermodynamic data from PC-SAFT for MDM based on these two fitting routes with experimental data show good agreement for both routes with a better performance in case of fitting to the extrapolation equations. Hence, PC-SAFT parameters were determined for all five siloxanes by fitting to the extrapolation equations. Comparisons of resulting PC-SAFT thermodynamic data with a variety of experimental data show good agreement. (C) 2009 Elsevier B.V. All rights reserved.