Ion-selective electrodes are widely used for non-destructive, rapid, sensitive and precise determination of many ions in a great variety of media and therefore, provide a powerful analytic tool. Since the appearance of the first edition of Professor Koryta's book in 1975 progress in the whole field of ion-selective electrodes has been rapid and a vast amount of diverse data has appeared. In this edition, based on the literature to mid-1981, a compact and unified treatment of the theory of ion-selective electrodes is presented along with an updated account of their analytical, biomedical and physicochemical applications. The book will be of interest to advanced undergraduate and graduate chemists, biophysicists, physiologists, biochemists and environmental scientists, as well as research workers in both universities and industry.