More than a year ago the three editors sat down at a table and worked out a set of six chapter headings which they believed might serve, in turn, for each of the three sections of this handbook. (The reader will note a similarity in order of presentation and in emphasis.) However, as our editorial plans progressed it became apparent that for each element and for the element group, there were one or two special topics appropiate for that section alone. Accordingly, in the section on uranium the common pattern holds for Chaps. 1 through 6 which include: an introduction (Chap. 1), a discussion of the physical and chemical properties (Chap. 2), experimental data on animals (Chap. 3), ex­ perimental data on man (Chap. 4), the rationale and development of air con­ centration limits to control industrial worker exposure (Chap. 5), and the prac­ tical problems of applying such limits in the uranium industry (Chap. 6). Chap. 7 entitled "Uranium Mining Hazards" is the subject category which is special for uranium; the chapter brings up to date the account of an important occupational hazard which was first noted by GEORGIUS AGRICOLA (1490-1555).