The first chapter of this multiauthor book is a unified treatment of the role and potential of new imaging methods using both ionising and nonionising radiations. (This provides a link with the first volume in this Surrey University Press series, which was concerned purely with ionising radiations). Jackson and Kouris tackle this difficult task by considering the generalised indirect sensing problem, the morphological and functional information of importance in medical diagnosis and the data obtainable by the various techniques dealt with in the following chapters. Chivers' discussion of ultrasonic imaging avoids repetition of well-known principles and concentrates on the analysis of acoustic wave propagation in tissues and the derivation of quantitative data.