The temperature-dependent moisture diffusion behavior of high-temperature polyimide resin, PMR15, is presented. Adsorption and high temperature desorption tests are used to experimentally determine moisture diffusivity at several temperatures. Diffusivity is determined from the weight change based on the initial slope and using a nonlinear regression technique with Fickian diffusion assumption. The basic test procedures and diffusivity values are presented in this study. The results also include the relative humidity (RH) dependent equilibrium moisture concentration and a relationship between the RH and equilibrium moisture concentration. As direct measurement at typical operating temperature may be precluded by blistering, an Arrhenius-type tempera ture-diffusivity relationship is used to estimate the temperature-dependent moisture diffusivity for the PMR-15 resin. The moisture diffusivity of PMR-15 tested is estimated to be 6.64 E -10 m (2)/s at 288 degrees C. (C) 2007 Wiley Periodicals, Inc.