Among the factors that may impede success in dental treatments, gingival biotype is the greatest cause of concern, particularly affecting the outcomes of periodontal therapy, root coverage procedures, and implant placement. Different tissue biotypes respond differently to inflammation and to surgical and restorative treatment; consequently, it is crucial to identify tissue biotype before treatment. Special care must be taken when treatment planning for cases with a thin gingival biotype. This article reviews the characteristics of various gingival biotypes and the many ways to determine them.