This article investigates environmental aging effects on thermal and mechanical properties of three model electrically conductive adhesives (ECAs). A combination of several experimental techniques including thermogravimetric analysis (TGA), water uptake measurements, dynamic mechanical analysis (DMA), and stress-strain dogbone testing has been utilized throughout this study. Samples were aged at 85degreesC and 100% RH for periods of up to 50 days, and some of the samples were dried at 150degreesC after aging. Results obtained on aged samples with and without drying suggest that the conductive adhesives may have experienced both reversible and irreversible effects during environmental aging. Both plasticization, which is reversible, and further crosslinking and thermal degradation, which are irreversible, are indicated upon exposure of ECAs to the hot/wet environment.