This Update follows on from last year's1 but covers a longer period. The system we use to access abstracts has been improved with the result that abstracts have become available more quickly and the review more timely. This review effectively covers a period of about 15 months up to the beginning of 2001. Although an attempt is made to consider all relevant refereed papers, conference abstracts, reports, book chapters and patents for inclusion, this review does not aim at being comprehensive in its coverage. 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. With the boundaries between atomic and inorganic molecular MS, and indeed organic MS, becoming less well defined, the judgement of the authors of this Update becomes important in considering papers for inclusion. The main ruling criterion for all papers is 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 are not covered in this Update and readers are referred to the Updates on Industrial Analysis: Metals, Chemicals and Advanced Materials,2 Environmental analysis3 and Clinical and Biological Materials, Food and Beverages.4 Becker and Dietze5 have produced yet another excellent review (210 references) covering in detail the inorganic MS techniques that are used for trace, isotope and surface analysis. Barshick et al.6 discussed the fundamentals and applications of inorganic MS in their substantial review. Although not focused specifically on MS techniques, the review (484 references) of Rao and Biju7 on the determination of REEs was interesting in that it presented most of its data in tabular form. The trends noted over the last few years have continued. In particular, the growing interest in speciation studies has been matched by the number of papers on the subject. The renaissance of GC-MS has continued and the niche of ESMS for species identification has been confirmed, in particular to complement the elemental information provided by ICP-MS. In all of these studies, sample preparation and introduction have generally received most attention with the aim of further improving analysis. The very wide range of applications of AMS was made apparent by the papers presented at a major international conference.8 The encroachment by ICP-MS into areas of traditional TIMS studies has continued with some success but ultimate levels of precision and accuracy can often only be achieved by the latter technique even if procedures are complex and time-consuming. A number of interesting trends were noted for ICP-MS in this review period. The use of LA, particularly for geological and environmental samples, continued to grow and has almost become a routine application. The use of collision or reaction cells for reduction/removal of polyatomic species has gained momentum and the use of both single- and multiple-collector magnetic sector MS systems has also increased significantly. There has been some interest in ICP-TOFMS systems, but it is not yet clear whether they offer any significant advantages over existing systems.