The in vitro antithrombotic properties of polar lipid microconstituents of three Irish beers (ale, larger, and stout) have been assessed against platelet-activating factor-induced platelet aggregation. Total lipid (TL) extracts were obtained using the Bligh and Dyer method and each beer was separated into the organic phase and hydromethanolic phase. The total polar lipid (TPL) and total neutral lipid (TNL) fractions of the organic phase and hydromethanolic phase of each beer were obtained using a counter-current distribution. The TL, TNL, and TPL extracts of each phase of each beer were measured for their capacity to inhibit platelet-activating factor-induced platelet aggregation. The low IC50 values obtained suggest that all three beers contain potent polar lipids that can inhibit platelet-activating factor-induced platelet aggregation. The fatty acid composition of the organic phase TPL extracts were measured using gas chromatography-mass spectrometry. The organic phase total polar lipid extracts were further fractionated using thin-layer chromatography (TLC) and the antithrombotic bioactivities of these TLC bands were measured. This data suggested that the TLC bands corresponding to phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, and cardiolipin were the most active phospholipids in the total polar lipids of the organic phase. These promising results indicate that beer consumption may provide antithrombotic effects.