Enamel craze lines are a common clinical finding, especially in older patients and in patients who brux. These craze lines frequently are discolored and may present as clear in color, grey, or brown. The clinical question is, when do enamel craze lines need restoration and when should we leave them untreated? This review will look at enamel structure and the effects of occlusion, bruxing, temperature, and restorations on enamel structure. Recommendations will be made on how and when to deal with these cosmetic defects of enamel.