This book really ought to be read on vacation, just for enjoyment. Granted, cancer is, literally, a deadly serious matter, and cancer research is primarily a part of medicine with Hippocrates in its back ground. Yet, cancer research is also natural science, and as such it yields the joys and sorrows of any science. The cancer problem is also a brain teaser, a challenge for the curious. This introductory report on experimental cancer research is there fore directed to curious students of many disciplines: naturally to medical students, but also to chemists and physicists who have an interest in biological phenomena; biology students will surely en counter pr9blems peculiar to their field in what is supposedly a medi cal one. We have attempted to write without assumptions to a certain degree, for a chemist is essentially in over his head in medicine, and a physician has only the slightest idea of the chemical problems im portant in cancer research. We had no intention of giving a complete view of the field, and from the large number of different lines of development we have chosen only a few. Chemotherapy, as an ex ample, has been treated quite cursorily, along with RNA tumor viruses, although it is possible that just these subjects are especially important for human tumors. Tumor induction via radiation could only be mentioned in passing, in spite of its great practical significance; similarly the role of hormones was only intimated.