AIM: To investigate whether antiplatelet agents, dilazep and dipyridamole, inhibit tissue factor (TF) expression on monocytes induced by IgG from patients with antiphospholipid syndrome (APS). METHODS: Freshly isolated peripheral blood monocytes were allowed to adhere on plastic and then cultured in media containing patient or control antibodies and/or other agonists with or without dilazep or dipyridamole. The TF activity on monocytes was investigated by measuring factor VIIa-dependent generation of factor Xa, using a chromogenic substrate and the TF mRNA expression was examined by real-time PCR (TaqMan PCR). RESULTS: The TF activity on monocytes induced by APS IgG (250 mg/L) was inhibited by dilazep (0.15-150 μmol/L) and dipyridamole (0.2-200 μrmol/L) in a dose-dependent fashion. But, the TF mRNA expression induced by APS IgG was not inhibited. Theophylline (500 μmol/L), an adenosine receptor antagonist, could counteract the inhibitory effect of dilazep and dipyridamole on TF activity. CONCLUSION: Antiplatelet agents, dilazep and dipyridamole, block APS IgG-induced monocytes TF expression at a post-transcriptional level, partly by adenosine receptor pathway. Pharmacological agents that block monocytes TF activity, such as dilazep and dipyridamole, are a novel therapeutic approach in APS.