It is a great pleasure for me to introduce and to recommend this much needed text on double contrast examination of the colon. It is aimed both at clinicians who request X-ray examinations of the colon and at radiologists who must per form and interpret these studies. Over the past decade there has been renewed interest in X-ray examination of the colon despite the tremendous advances in endoscopy and imaging tech nology. This renewed interest is evidenced by the proliferation of new books on radiology of the colon. However, previous discussions of double contrast ex amination have concentrated primarily on the technique with too little attention to the understanding and interpretation of the radiologic images. This volume is unique in its emphasis on the basics of image formation and interpretation. It emphasizes the importance of the anteroposterior relation ships of the colon in determining the distribution of barium and air. It also rec ognizes the influence oflocation on the radiologic appearance of the lesion. The authors demonstrate a profound understanding of the principles of double contrast diagnosis as applied to the colon. They also have a good grasp of the gross pathologic changes underlying the radiologic images. The material is presented in a logical and analytical method which should be particularly useful to the beginner in this field. There are many helpful diagrams and the ra diographic illustrations are of excellent quality.