Structural silicone sealants have been used since the mid 1960s in the construction industry to attach glass to curtainwall framing systems. Design standards for these sealants have been in practice since the early 1970s and continue to be developed today. Most of these standards require tests that are based on a one-time destructive test of the joint material in tension. The industry established structural silicone design stress is intended to be reached only during the highest windload for the speci.ed return wind period. The existing practice has had great success because the industry guidelines minimize stress on the silicone, and dictate quality assurance procedures that are instituted by curtainwall producers. In real life situations the sealant is additionally fatigued through a cyclic shear mechanism caused by daily thermal movement differences between the glass pane and the aluminum frame. This paper discusses a method for testing the effect of fatigue in sealants used in structural designs and comparing the data to control samples.