The combination of Etch-Free Primer and C&B Metabond has been reported to produce high resin composite to feldspathic porcelain bond strengths without hydrofluoric acid etching. This study compared the shear bond strength of resin composite to a castable glass ceramic that was treated with either Etch-Free Primer and C&B Metabond or ammonium bifluoride (NH5F2) etch/silane under various surface treatment and thermal stress variables. Bond strengths after Etch-Free Primer/C&B Metabond treatment were significantly lower than those for NH5F2/silane treatment. Thermocycling was the most important variable in reducing Etch-Free Primer/C&B Metabond bond strengths.