The pyroelectric behaviour of cellulose acetate polymer films was studied in a vacuum of 10-3 torr under a polarizing field strength range of 6.25 × 105-50 × 105 V/m and a polarizing temperature range of 304-406 K. The pyroelectric coefficient exhibited abnormal behaviour, starting initially on the negative side and then changing sign from negative to positive. Negative coefficients are believed to be due to dipolar orientation, whereas space charge polarization is responsible for positive pyroelectric coefficients.