The temperature dependence of the specific volume, V, and of the mean size of local free volumes (holes), nu(h), of poly(vinyl chloride) containing 10 wt% (PVC-h) and 30 wt% (PVC-s) of the plasticizer di-n-butyl phthalate (DBP) were studied by pressure-volume-temperature (PVT) and positron annihilation lifetime spectroscopy (PALS) experiments. Using the Simha-Somcynsky equation-of-state, the hole fraction h was calculated from the PVT data. It was found that the thermal expansivity of the specific volume V, the specific free volume V-f = hV, and nu(h) increase with the content of plasticizer. From the comparison of V and V-f with nu(h) the hole number per gram N-h' is estimated. Other than nu(h), N-h' does not depend on the temperature nor on the content of plasticizer. (C) 2003 Elsevier Science Ltd. All rights reserved.