Proton magnetic resonance (PMR) spectrometry supplements optical spectroscopy and gas chromatography in the identification of organic archaeological materials. PMR establishes the average chain length and unsaturation of fatty acids. An oil sample of the sixth-fourth century B.C. Is shown to consist largely of oleic acid. A solid fat of the third century A.D. Contained principally myristic and palmitic acids. The absence of measurable glyceryl signals shows both samples were at least 95% hydrolyzed. PMR spectra also indicate that the pyrolysate of Baltic amber contains significantly less p-cymene than that of modern pine resins, confirming previous evidence that abietane structures are only a minor component of the fossil resin.