To evaluate the influence of permeant and temperature exposure on the state of stress in polyimide coatings, uniaxial experiments on thin polyimide films held at constant length were performed. The uniaxially constrained poly(4,4′,-oxidiphenylene pyromellitimide) or PMDA-ODA films were exposed to methylene chloride while the stress was monitored. It was found that the stress was reduced to zero from a stress as high as 40 MPa by the swelling with methylene chloride. Attempts to remove the methylene chloride at room temperature with a nitrogen purge resulted in a stress increase of only 8 MPa. However, the remaining stress of an additional 20 Mpa was recovered when the sample was heated to 350°C and returned to room temperature. Temperature exposures of 150°C and 200°C resulted in a stress increases of only 14 MPa and 17 MPa, respectively. These observations suggest a strong coupling between the stress state, temperature and equilibrium swelling by permeants.