Positron annihilation lifetime and Doppler broadening of annihilation radiation studies of pure and doped polyvinyl chloride (PVC) with Al(2)O(3) reflect the effect of concentration on free volume. Therefore, variations of the relative fractional free volume, which is extracted from positron annihilation parameters, have been correlated with changes in the dielectric properties (dielectric constant and a.c. conductivity) of the pure and doped PVC with Al(2)O(3) from 10 to 50%. The o-Ps lifetime and its intensity show a linear dependence with a discontinuity at 30% concentration of Al(2)O(3). A correlation between the relative fractional free volume and the dielectric parameters has been achieved.