Exposure to environmental factors, especially moisture, is recognized as the major cause of degradation of adhesive joints. In this work, complementing a previous study on exposure to moisture, single lap joints were subjected to immersion in water, up to five weeks, at room temperature and 50 degrees C. The material of the adherends was mild steel, and the adhesive was a bi-component epoxy. The specimens were fabricated using the open-face technique. Mechanical testing at the end of the relevant period of immersion showed an initial loss of ultimate load, after one week at 50 degrees C or two at room temperature; then, the strength remained practically constant over the remaining time. The loss was more accentuated after immersion at 50 degrees C, about 70%, than at room temperature, about 30%. Also a reduction in stiffness of the joints was measured, again dramatic (about 70%) after immersion at 50 degrees C, moderate (about 10%) after room temperature immersion. Optical examination, performed before closing the open-face specimens and after mechanical testing, showed that the major damage mechanism was the formation of blisters filled by liquid at the primary adherend/primary adhesive interface, causing the failure mode to change from cohesive to interfacial.