Predictable tooth whitening requires proper diagnosis and understanding of discoloration to manage patient expectations. Success goes beyond product selection, demanding a comprehensive grasp of stain types (intrinsic vs. extrinsic), causes (age, fluorosis, tetracycline), and precise shade assessment. Accurate identification of the stain dictates the correct treatment choice (in-office, take-home, or combination). This lecture covers diagnosis, system selection, managing common pitfalls, enhancing patient compliance, and techniques for long-lasting results. This knowledge empowers clinicians to make informed decisions for optimal, predictable aesthetic outcomes.