3'-(4-[2-(1-P-Chlorobenzoyl-5-methoxy-2-methyl-indol-3-yl-acetoxy)-ethyl]-piperazin-1-yl)propyl-4-benzamido-N,N-dipropyl-glutaramate(+/-)dimaleate (protacine, CR 604), a new non-steroidal compound active on experimental inflammation, in vitro inhibits prostaglandin synthesis from arachidonic acid and platelet aggregation. When administered p.o., it prevents ex vivo platelet aggregation and in vivo arachidonate-induced thrombosis in rabbits. The cAMP levels of rat leucocytes are significantly reduced after treatment in vivo with protacine, even under maximum PGE-mediated stimulation. These effects, the inhibition of the proteolytic activity of trypsin and the fibrinolytic properties evidenced on recalcified plasma clots, contribute to explain the anti-inflammatory activity of protacine.