Phenolic resins are added to rubber compounds to improve the tack (or autohesion) characteristics. These resins are generally oligomers of alkylated phenols and formaldehyde. Analytical characterizations of these resins are very limited and incomplete in the open literature. We have examined several types of resins using mass spectroscopy (principally field desorption, FD-MS), liquid chromatography (LC), and infrared spectroscopy (ATR-IR). Several oligomeric series were identified by FD-MS in t-octylphenol and t-dodecylphenol resins. ATR-IR analysis showed that the t-octyl groups are essentially completely p-substituted on the phenolic ring. LC was only of limited utility in obtaining analytical separations of resin oligomers. Higher molecular weight oligomers (≿1500) showed little if any LC resolution. Resins prepared under different manufacturing conditions showed additional series of oligomers. These were either “cyclic ethers” and/or amine-containing compounds, depending on the synthetic procedures used.