Frequently attempts to design experiments utilizing the methodology de­ scribed in articles in trade journals can be frustrating. Description of procedures, because of space constraints, are not always complete. The present volume attempts to bring together in one reference source many of the techniques which are utilized in the study of the kidney. It provides a thorough compendium of research tools, framed by the critical analysis of the theoretical background of renal physiology, biochemistry, and pharmacology discussed in Volume 4A. Some areas previously dealt with are not covered from a methodological point of view since adequate information does exist elsewhere (e.g., methods of whole kidney ATPase isolation). Since drugs acting on the kidney may alter not only functional but anatomical integrity, a chapter on the preparation of tissue for morphological studies has been included. The important developments in analysis of minute (ultramicro) quantities of tissue and biological fluids, as well as methodological advances in studies of the isolated kidney, are thoroughly covered. It is my hope that investigators, research fellows, and graduate students will benefit from the information contained in this volume and that, together with its companion tome, it will be a ready reference for the renal physiologist, the renal pharmacologist, and the nephrologist. The contributors have provided painstaking descriptions and, when required, mathematical analyses of the techniques described herein. I wish to thank all of them for their enthusiasm and the excellence of their contributions.