Successful treatment of cancer often requires compromises on the part of both doctors and patients. One such concession is the young patient’s permanent loss of reproductive capacity, which has frequent long-term psychological consequences. Cancer patient fertility is the subject of a new medical field called oncofertility. This new medical discipline expands cooperation among embryologists, biologists, oncologists, sociologists, and reproductive medicine specialists. In this book readers will become informed about the basic principles of this new medical discipline. They will become aware of recent molecular biology research in terms of potential clinical applications. We will also discuss certain legal, ethical, and social aspects related to this new and fascinating knowledge. This work defines oncofertility as a new direction in reproductive medicine. It summarizes the latest findings and tries to predict successful discoveries and further advancements in this exciting multidisciplinary field. Hopefully the book will attract readers and inspire associates to become further involved in improving the quality of life of cancer patients whose future fertility has been severely compromised.