The field of isotope geochemistry continues to grow at an unprecedented rate. As such, it becomes more difficult each year to provide a comprehensive over- view. In preparing this review many hundreds of papers were considered from approximately twenty journals in an attempt to provide an (admittedly small) window in time on this inexorable march of progress. The previous two commentaries in this series (Woodhead 2005, 2006), covering the years 2003 and 2004-2005, examined the changing roles of the benchmark methodology for isotope ratio determina- tion – thermal ionisation mass spectrometry (TIMS) – and the newly emergent multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) instrumenta- tion. In just a few short years it is probably true to say that this drama has now been largely played out and that, as far as is reflected in the literature, MC-ICP-MS technologies have come to dominate the analytical landscape, largely as a result of their comparative ease of use and enormous flexibility. Significant analy- tical issues still remain with this nascent technology, some of which will be touched upon in the following text but, for the most part, the trend towards wides- pread dominance of MC-ICP-MS (and a diminishing role for TIMS) seems clear. As a result, the emphasis in this article is on the many and varied applications of these new technologies. Also, in the period covered by this review, we see significant new drivers of research output, in particular the considerable uncertainty presented by the threat of global climate change. Scientists have of course always taken a keen interest in the Earth’s changing climate but, in recent years, the subject has gained greater public exposure and thus inevitably finally impinged upon the political psyche. Enhanced awareness of the problem and rush to find solutions has resulted in improved funding for some avenues of research and this, in turn, has led to a significant increase in publications in areas such as palaeoclimate and oceanography. Concurrently, many traditional disciplines (e.g., petrology) have been adversely affected by government funding strategies, which are increasingly directed toward applied research, and output has dropped when compared with previous years. Oceans, climate and the environment The oceans are inextricably liked with our unders- tanding of climate and environmental change, and are thus considered here within this single broad theme. Taken together, this is an area that has seen a phenomenal increase in research interest over the past few years. As such, it is impossible to do full justice to the subject here and only a handful of the many avai- lable papers are represented. Isotope Ratio Determination in the Earth and Environmental Sciences: Developments and Applications in 2006-2007 Vol. 32 — N° 4 p.495-507 495 12 08 Jon D. Woodhead School of Earth Sciences, The University of Melbourne, VIC 3010, Australia e-mail: jdwood@unimelb.edu.au © 2008 The Author. Journal compilation © 2008 International Association of Geoanalysts Received 31 Oct 08 — Accepted 12 Nov 08 GEOSTANDARDS and RESEARCH GEOANALYTICAL This review documents developments and applications in the field of isotope ratio determination, as reflected in the literature for the Earth and Environmental Sciences for the years 2006 and 2007. The emphasis is predominantly on applications, reflecting the enormous diversity of problems to which isotopic analysis can now be applied, but viewed in the context of rapid uptake of new analytical technologies and significant new drivers of research output. Keywords: review, isotope ratios, thermal ionisation mass spectrometry, multi-collector ICP-MS.