Abstract: This Update is part of a series of annual reviews which cover the various aspects of analytical atomic spectrometry. John Williams has contributed to the ICP-MS section of all 17 of the reviews since the inception of the series in 1988 but is unable to continue to do so. We wish to acknowledge his valuable contribution over the years and to thank him for his efforts. We welcome Kathryn Linge to the writing team in Johns place. This years review follows the same format as last years but there has been some re-ordering of the sections to reflect the growing importance of ESMS and GC-EIMS for speciation analysis. Although an attempt is made to consider all relevant refereed papers, conference abstracts, reports, book chapters and patents for inclusion in this review, the content of the review is highly selective. The selection of papers is based on criteria applied to focus sharply on the most significant developments in instrumentation and methodology or improved understanding of the fundamental phenomena involved in the MS process. The increasing importance of speciation and the blurring of boundaries between atomic and molecular MS require a high degree of judgement to be made in considering papers for inclusion. The main criterion for selecting speciation papers was that the work should involve or be intended for the study of natural systems. For example, the study of synthetic metal clusters is generally not included, whereas the determination of organometallic compounds in environmental samples is. Applications of atomic MS in other areas are not covered in this Update and readers are referred to the Updates on Industrial Analysis: Metals, Chemicals and Advanced Materials, Environmental Analysis and Clinical and Biological Materials, Food and Beverages. Throughout this review, the term molecular ion will be restricted to denote only the positive or negative radical ion formed by removal or capture, respectively, of an electron. In contrast, addition of a proton or cation to a neutral molecule gives a molecular adduct ion. Deprotonated molecules are considered as fragments. Although reproducibility or precision is a key figure of merit in MS, there is no agreed format for quoting it. The reader can assume that values of precision given in this Update as a percentage correspond to the RSD unless otherwise specified. For isotope ratios, however, values of precision are generally given as the SD of a permil value. It is a widespread phenomenon that analytical techniques in general, and MS in particular, spawn a large number of abbreviations and acronyms. A glossary of all abbreviations used in this Update appears at the end of the review. Most abbreviations are not defined in the text but those which are unlikely to be commonly known are defined in the text when used first and again in the glossary.