An investigation into the nondestructive monitoring of the environmental degradation of composite adhesive joints is presented. Three classes of joints, representing a variety of interfacial properties due to different pretreatments, were exposed to circulating hot water. Periodically thereafter specimens were weighed, subjected to an ultrasonic A-scan, and destructively tested to assess the breaking-loads and modes of failure. Statistical feature based analysis was conducted to correlate ultrasonic features to the amount of water soaked by the joints and the corresponding changes in their initial breaking-loads. The sensitivity of the ultrasonic features to the quality of the pretreatment provided to the joints was statistically tested as well.