The book is intended as that introduction to the ICP-OES technique. It was written not only for those persons who have some familiarity with other analytical techniques such as atomic absorption spectrometry but also for novices in the field of analytical chemistry. The book begins with some simple, yet fundamental, concepts regarding atomic spectroscopy and the analytical techniques based on this field of study. As one progresses through the book, more detail regarding the ICP-OES technique is presented including information about ICP-OES performance, instrumentation and methodology. We have also included some information about instrument maintenance and performance verification. While this kind of practical information can be vital to obtaining good analytical results, it is sometimes difficult to find. We hope that this book will provide useful information to those persons who are about to get involved with ICP-OES as well as present ICP users and those with simply a curiosity about the technique.