Introduction. Organic materials that survive in archaeological contexts often have a polymeric nature which is either intrinsic or results from prior decomposition leading to polymerization. While polymeric character may enhance survival by increasing resistance to environmental attack it also poses many problems of analysis and identification because of the often intractable nature of the materials. We report the analysis of examples of such residues -- plant resins -- with esr and ¹³C-nmr spectroscopy and show how these techniques can give information both on structure and on deterioration that is of interest to archaeologists. The ¹³C-nmr of ancient resins has been discussed previously but, whilst esr has been used to study archaeological samples, this article is the first to report esr measurements on such materials. -- CCI