The studies on photoplastic effect of polycarbonate has helped significantly in understanding the elastoplastic behavior of polycarbonate. When a plastically deformed specimen (polcarbonate) is suddenly illuminated with light of proper wavelength, a decrease in flow stress is observed, deformation leads to the softening, of specimen, i.e., to the negative photoplastic effect obtained at room temperature. On switching off, deformation stress reaches its level in the dark. The studies on the negative photoplastic effect mechanism can offer ways to control the properties of photoelectronic devices. (C) 2003 Wiley Periodicals, Inc.