Metal ceramic restorations are popular in restorative dentistry. Although bonding mechanisms are understood, defining compatibility of alloy and porcelain has been illusive. Chemical compatibility implies a chemical bond between ceramic and alloy that resists stresses resulting from thermal and mechanical incompatibility without compromising esthetics. Research has attempted to predict and test compatibility with varying degrees of success. Despite the success of metal ceramic restorations over the years, compatibility remains undefined without standardized testing procedures. For optimal results, the dentist should communicate with experienced laboratory personnel to meet the specific needs of the patient.