The main aim of this study was to determine how the residual solvent remaining after fabrication affected the gas permeation properties of 6FDA-mPDA polyimide films. For this purpose, films were made by spreading solutions of polyimide from different solvents on glass plates, then treated at 200 degrees C for different periods of time. The films obtained were characterized by differential scanning calorimetry, thermogravimetry and permeametry. Permeation parameters (D, P, S) of the films towards N-2, and CO, were determined at 35 degrees C. They were found to be dependent on the residual solvent in the films. Whatever the solvent, the difference in behaviour was found to decrease as the amount of solvent became smaller and to increase with the molar volume of the solvent. Solvents with high molar volumes left an imprint in the material during thermal treatment.