What to do in the case of…? is a thoracic transplant-oriented Guidebook for the initial evaluation and diagnosis of common syndromes in cardiothoracic transplant recipients. This manual has been written by a wide international representation of authors with different areas of expertise, to give a multifaceted response to a broad range of clinical syndromes encountered after cardiothoracic transplantation. This project has been designed as an educational and practical tool for physicians, involved or not in the transplant field, to improve the management of transplant recipients. Indeed, delays in accurate diagnosis can lead to increased morbidity and mortality in this population. The manual has been structured in 11 sections, each divided into different chapters dealing with a general topic. Each chapter includes the most frequent etiologies of a clinical syndrome or finding, together with different diagnostic tests according to their priority in a transplant recipient. Every chapter has been written by two authors, at least one being an expert in the field of transplantation or infectious diseases. In addition, as a new diagnostic educational tool, each chapter has been reviewed by four different experts in the field of transplant.