The Encounters and Transformations in Iron Age Europe project (ENTRANS) aims to expand our knowledge regarding the nature and impact of cultural encounters during the European Iron Age. The study of ceramic vessels was included in the project, in order to further understand cultural practices in the south-east Alpine region. Organic residue analysis is an important tool in archaeological research for determining the presence of food and other organic substances associated with ceramic vessels. It has the potential to significantly improve our understanding of Iron Age societies and the interactions between them. This research focuses on the analysis of visible and absorbed organic residues from 377 ceramic vessels, from Late Bronze Age and Early Iron Age sites in Slovenia and Croatia, by gas-chromatography mass spectrometry. Two methods of lipid extraction were compared in a pilot study compressing 30 potsherds from Kaptol (solvent vs. acid extraction). This study revealed that more information was obtained by acid extraction, thus it was selected as the main method of extraction for this project. Differences between settlement, funerary and ritual sites were observed, suggesting that the vessels placed in the graves were not previously used or carried foodstuff with low lipid content, such as liquids and dry foods/cereals. Some types of residues were only identified in funerary vessels, specifically potential castor oil in Kaptol, mixed with other fats and oils. Lipid biomarkers and lipid ratios revealed significant differences between contexts and different sites, suggesting that the differences in cultural practices can also be identified in the use of ceramic vessels. Some residues were also sampled for gas-chromatography compound-specific isotope ratio mass spectrometry and bulk isotope analysis (only visible residues), which identified potential dairy fats in two potsherds from Poštela. The results were also compared with the contextual information, mainly the faunal remains, and the data obtained from the osteology and diet study preformed with individuals from the same area and chronology as the ceramic vessels. / Encounters and Transformations in Iron Age Europe Project (ENTRANS); Humanities in the European Research Area (HERA); Institute Life Sciences Research (ILSR) University of Bradford.