Isothermal acetone absorption in UV-irradiated polycarbonate (PC) was investigated at temperatures from -23 to +25 degrees C. The crystalline fraction of PC increased with UV dose. The anomalous transport data were analyzed based on Harmon's model which includes contributions from Case I transport characterized by the diffusion coefficient, D, and Case II transport characterized the velocity, v. Diffusion coefficients were monitored by both mass uptake using the model (D and v), and movement of the sharp front (D-f). Plots of log of D, v, and equilibrium swelling ratio (ESR) versus 1/T exhibited similar features. That is, plots were linear and superimposable for all doses at the higher temperatures, and exhibited a transition temperature and then a linear region that varied with dose. The values of D, D-f, and v increased with increasing dose, whereas the ESR decreased with dose. The direction of Case II transport was opposite to that of Case I diffusion during which time, sorbed solvent was expelled from the samples. Results are discussed in terms of a solvent-induced change in lattice structure at the lower temperatures and in terms of UV radiation effects on the PC matrix that enhance solvent crystallization. POLYM. ENG. SCI., 58:1174-1183, 2018. (c) 2017 Society of Plastics Engineers