The piezoelectricity and charge storage in unstretched corona poled poly (styrene-co-acrylonitrile) films have been investigated under different poling conditions. The piezoelectric coefficient d(31) has been measured as a function of poling field ( Ep) and poling temperature (T-p) and the maximum value of d(31) congruent to 1.0 pC/N has been obtained at E-p congruent to 46 MV/m and T-p = 85 degrees C. The Frolich equation for dipolar polarization has been applied for quantitative analysis of the thermally stimulated current (TSC). The g-factor = 1.7 has been obtained, suggesting cooperative dipolar relaxation. The Young＇s modulus has been measured to be congruent to 0.45 GPa. The dipolar polarization from the TSC and the elastic modulus of the films have been correlated to the piezoelectricity through the modified equation for d31 for amorphous SAN films. It has been concluded that the mechanisms of the dimensional and the local field effects are involved in the piezoelectric phenomenon.