Abstract: Acetylsalvianolic acid A (ASAA) has been shown to be an antiplatelet compound. Our studies with RIA showed that: at the dosage of inhibiting platelet aggregation, ASAA was found to inhibit the formation of cyclooxygenase pathway metabolites TXB₂ in platelets. In addition, ASAA was also shown to promote the formation of 6-keto-PGF_1α in rabbit aortic rings in vitro. The above results suggest that ASAA may inhibit the proaggregator TXA₂ formation, promote mildly the antiaggregator PGI₂ generation and probably, whereby, exert its antiplatelet activity.