It might be asked if there is a need for yet another large review on Intestinal Absorption, and the answer is that this is still a rapidly expanding field of interest both from the medical and scientific points of view. There is ample evidence for this in the number of papers which continue to be published, and the bul­ letin on Intestinal Absorption issued by the Biomedical Infor­ mation Project of the University of Sheffield lists about 150 titles per month, and there is still no sign of any diminution in this rate. There are in fact so many papers that those interested in intestinal absorption have to be specialists in one particular field, but must at the same time be aware of the general deve­ lopments in the subject as a whole. The last major review was the excellent volume in the American Handbook published in 1968, already six years ago, and indeed a number of the con­ tributors to that volume have taken part in the present work. Some observations made in the introduction to a volume of the British Medical Bulletin on Intestinal Absorption some years ago are still pertinent. Progress in the experimental sciences is not continuous, but proceeds in phases of rapid expansion alter­ nating with periods of slower growth.