Essential omega-6 (n6) and omega-3 (n3) polyunsaturated fatty acids (PUFA) may undergo enymatic or free-radical mediated oxygenation to form a wide array of biologically active lipid mediators. These mediators play pivotal roles in the regulation of inflammation; n6 prostaglandins, thromboxanes and leukotrienes are key regulators of the pro-inflammatory response and, it is now widely accepted, that n6 lipoxins, together with n3 resolvins, protectins and maresins (collectively known as specialised proresolving mediators, SPM) are involved in the resolution of inflammation. In general, the clinical measurement of lipid mediators are made using targeted tandem mass spectrometry coupled with liquid chromatography (LC-MS/MS). However, issues surrounding the chemical stability of these species, their fast metabolic degradation and the potential for artefacts or auto-oxidation product formation during plasma collection, storage and extraction lead to queries about the presence of certain lipid mediators, in particular SPM, in plasma. In addition, the effect of dietary or pharmaceutical supplementation on plasma lipid mediators levels is largely debated. In the present study, we describe the stability of selected mediators in human plasma when stored at -80°C for a least one month, their LC-MS/MS detection in plasma from healthy volunteers and the effect of aspirin supplementation on these plasma profiles.