Effects of hydration on silk fibroin film properties were investigated for water-annealed and MeOH-treated samples. Hydration increased thickness by 60% for MeOH-immersed films, while water-annealed samples remained constant. MeOH-immersed films showed an 80% mass loss due to water, while water-annealed lost only 40%. O(2) permeability was higher in MeOH-immersed films with Dk values of 10(-10) (mL O(2) x cm) x (cm(-1) x s(-1) x mmHg(-1)), while those of water-annealed films reached only one fifth of this value. All films showed a decrease in Young's modulus and increased plastic deformation by two orders of magnitude when submerged in saline solution. FT-IR showed that beta-sheet content in water-annealed films increased with increasing water vapor pressure, while MeOH-immersed films showed no change.