Conductive adhesives are used in electronics packaging applications for hybrid, die-attach and display assemblies. There are a number of issues of concern in the design of joints bonded using electronically-conductive adhesives (ECAs). An important issue is the cyclic fatigue behavior of conductive adhesive joints under elevated humidity environments, in which failures may occur due to cyclic mechanical and/or thermal stresses. This paper addresses the effect of elevated humidity levels on the fatigue and failure behaviors of ECAs. For this purpose, joints were prepared using stainless-steel adherend specimens and a commercial ECA, and tested under monotonic and cyclic fatigue conditions, at two humidity levels, namely 20% and 90% relative humidity at 28 degreesC. Furthermore, joint failure mechanisms were analyzed using optical techniques, and joint conductivity measurements. Load versus number of cycles (P-N) curves were generated using these specimens at three different load ratios (R), namely 0.1, 0.5 and 0.9, at a cyclic frequency of 150 Hz. The P-N curves were parallel and the failure modes were found to be predominantly interfacial, accompanied by a significant decrease in joint conductivity.