The first edition of the Forensic Isotope Ratio Mass Spectrometry (FIRMS) Network's Good Practice Guide for Isotope Ratio Mass Spectrometry was published in 2011.1, 2 This document was the result of a collaboration between members of the FIRMS Steering Group and the UK's National Measurement System and was edited by Jim Carter (then Chair of the FIRMS Network) and Vicki Barwick of LGC Limited (formerly the Laboratory of the Government Chemist). Both the FIRMS Network and LGC believe that good practice in isotope ratio analyses is desirable regardless of application, and therefore the first edition of the Guide was made freely available. The Guide has clearly been a valuable resource to the stable isotope community having been downloaded many hundreds of times per year and increasingly being cited in research articles.