This book is based on the proceedings of a symposium sponsored by the American Society of Zoologists, held during the society's San Francisco meeting (27–30 December 1988). Arguably, most physiological symposia focus, with varing degree of specificity, on issues within a classical division of the subject. This traditional approach has been, and continues to be, worthwhile and fruitful. However, the impetus here was to take a general theme (efficiency) and explore it broadly from a variety of perspectives and fields. The general consensus of opinion of the participants and audience at the San Francisco meeting was that the symposium was successful and worthy of publication. The resulting book consists of ten chapters (contributed by the symposium speakers) which vary somewhat in depth of coverage, length, style, and organization. This reflects a conscious decision on my part not to strive for uniformity through ‘heavy handed’ editing. A brief outline of the book's structure and content follows.

Chapter 1 (C. Gans) establishes definitions for a variety of terms (e.g. adequacy, efficiency, optima, perfection) that are employed by some authors in subsequent chapters. Gans discusses these concepts in the context of evolutionary biology, bearing on adaptation, development, and speciation. This issue is returned to in Chapter 10 (G.V. Lauder) where it is argued that concepts of efficiency may be used in integrating the discipline of physiology with historical biology. In Chapter 2 (R.W. Blake) the influence of the choice of formalism, interpreting high and low values, and the relevance of laboratory results to field situations are considered for efficiency criteria in physiological systems.