This book examines the medical significance of electrolytes, acids, bases and blood gases, and how they are determined. It was written to provide physicians with a snapshot of the analytical testing of electrolytes, acids, bases and blood gases. In addition, it provides laboratory technicians with an overview of physiology and pathophysiology in these fields. The first part of the book provides a summary of the current status of diagnosis and therapy. It can be used for quick reference at the - tient’s bedside or to more thoroughly research pathophysiological int- dependencies. A separate section is dedicated to electrolytes in urine. The latter chapters discuss the preanalytical and analytical testing of electrolytes, the acid-base balance and blood gases, with special cons- eration for performing determination using ion-selective electrodes and carrier-bound reagents (“dry chemistry”). The final chapter discusses the quality assurance of the methods, with consideration for the new Guidelines of the German Bundesärztekammer (2001), which are p- sented in outline form.