1) Edmund Mach Foundation, IASMA Research Center, Agrifood Quality Department, via E. Mach, 38010 San Michele all’Adige (TN), Italy, 2) Isolab GmbH, Laboratorium für Stabile Isotope, Woelkestrasse 9/I, 85301 Schweitenkirchen, Germany Rapid Communications in Mass Spectrometry (2009), V23, pp1043–1048, doi: 10.1002/rcm.3968 Coast and year effect on H, O and C stable isotope ratios of Tyrrhenian and Adriatic italian olive oils L. Bontempo (1), F. Camin (1), R. Larcher (1), G. Nicolini (1), M. Perini (1) and A. Rossmann (2) The paper discusses the 2H/1H, 18O/16O and 13C/12C ratios of 196 authentic Italian extra-virgin olive oils produced in 3 years on the Tyrrhenian and Adriatic coasts. The 2H/1H and 18O/16O ratios were linearly and positively correlated. The year of production influenced mainly 18O/16O in relation to the amount of rainfall and the atmospheric humidity in the period of oil accumulation in the olives. The 2H/1H ratio significantly distinguished the olive oils produced on the Adriatic coast from those on the Tyrrhenian coast in each year. This coast effect is a consequence of the different sources and isotopic compositions of the rainfall and the different climatic conditions on the two coasts. The paper contributes towards understanding the influence of climatic factors on isotopic variability and towards improving the traceability of the geographical origin of olive oils, using 2H/1H as a more innovative parameter.