The practical application of the sentinel node concept is evaluated in this book. The concept is analyzed for breast cancer, malignant melanoma, tumors of the face, oropharynx, lung, gastrointestinal and urogenital tract. The first part of the book describes the function and use of the nuclear medicine equipment, the tracers used, colloid solutions and modern developments in histological and immunohistochemical lymph node investigations, as well as possible pitfalls. In the second part, specific tumor-related problems are described.