Oscillations are everywhere in biology¿the heart beat, circadian rhythms, fertility cycles¿life could not exist without them. Thanks partly to the discovery of oscillations in biochemical pathways, oscillating reactions reached the status of a branch of laboratory chemistry in the early 60`s. Since then, theoretical and experimental studies of oscillating reactions have been carried out in many laboratories, and the interest in this type of phenomena is increasing very rapidly, since the phenomena involved are occasionally counterintuitive and often aesthetically pleasing. In the last decades, several studies have been published that show the potential of these reactions in analytical-based determinations. Applicability of the oscillating reactions for this purpose arises from their inherent complexity and extreme sensitivity to various perturbations. This book devotes special attention to practical aspects of oscillating chemical reactions in analytical chemistry. It deals with oscillating chemical reactions including Bray¿Liebhafsky (BL), Belousov¿Zhabotinskii (BZ), Orban, and peroxidase-oxidase oscillatory reactions used so far for analytical monitoring purposes.