The literature analysis of stillingia oil, which has recently been shown to contain an abnormal spectroscopic component, does not accord with its excellent drying properties. In a re-examination of a number of commercial samples the abnormal component is shown to be 2: 4-decadienoic acid, present to the extent of 3% to 6%, and hitherto undetected in naturally occurring oils. This component behaves anomalously during analysis by alkali isomerization, but the effect can be allowed for and the remaining components of the oil are estimated approximately at 40% linolenic, 25% to 30% linoleic, 20% oleic and 9% saturated acids, together with a little conjugated triene acid of the elaeostearic type which is possibly an adulterant. The 2: 4-decadienoic acid may play a relatively prominent part in the drying and polymerizing properties of stillingia oil.