Within the framework of an Italian research project aimed at studying organic residues found in archaeological objects from the Roman period, the chemical composition of the contents of several glass vessels recovered from archaeological sites from the Vesuvian area (Naples, Italy) was investigated. In particular, this paper deals with the study of an organic material found in a glass bottle from the archaeological site of Pompeii using a multi-analytical approach, including FT-IR, direct exposure mass spectrometry (DE-MS) and GC-MS techniques. The overall results suggest the occurrence of a lipid material of vegetable origin. The hypothesis that the native lipid material had been subjected to a chemical transformation procedure before being used is presented and discussed.