This book examines three harvests of virgin olive oils (VOOs) from the Mediterranean basin which were analysed by 1H-NMR and 13C and 2H isotope ratio mass spectrometry (IRMS) to determine their geographical origin at the national, regional or PDO level. An increase in 13C/12C and 2H/1H ratios was observed in VOOs from northern to southern regions; VOOs produced in France and northern Italy presented higher values than those produced in Spain and Greece. This trend was also observed in VOOs from northern and southern Italy, and for those from southern Spain and the other Spanish regions.