The textbook "Clinical and Diagnostic Pathology of Graft-versus-Host Disease" offers a comprehensive analysis of Graft-versus-Host Disease (GvHD), which often occurs as a complication of allogeneic stem cell transplants. GvHD can affect various organs such as the skin, liver, and gastrointestinal tract, and has the potential to lead to severe or even fatal outcomes. The diagnosis of this condition relies on clinical and histomorphological parameters. However, given the increasing use of GvHD prophylaxis, it is necessary to update diagnostic approaches, as typical histological features are becoming less common and atypical or masked lesions are occurring more frequently. This book describes the histological characteristics of GvHD lesions under current conditions and highlights differential diagnostic challenges as well as histodiagnostic pitfalls. Additionally, it discusses the applicability and limitations of immunohistological methods for diagnosing GvHD.