A first aspect of the present invention is a blood platelet preparation comprising blood platelets, an adenylate cyclase stimulator, a phosphodiesterase inhibitor, a thrombin inhibitor, and a plasmin inhibitor. A second aspect of the present invention is a plasma-free platelet storage medium containing dextrose, sodium citrate, sodium bicarbonate, and a platelet activation inhibitor, with a preferred platelet activation inhibitor comprising an adenylate cyclase stimulator in combination with a phosphodiesterase inhibitor. A third aspect of the present invention is a process for producing a plasma-free platelet preparation comprising producing platelet-rich plasma (PRP) from whole blood, adding a platelet activation inhibitor thereto, centrifuging the PRP to deposit the platelets on the bottom of the centrifuge container, removing the platelet-free plasma supernatant therefrom and adding a plasma-free liquid platelet storage medium thereto. A preferred platelet activation inhibitor for the process comprises an adenylate cyclase stimulator in combination with a phosphodiesterase inhibitor.A preferred adenylate cyclase stimulator is Prostaglandin El, a preferred phosphodiesterase inhibitor is Theophylline, a preferred plasmin inhibitor is Aprotinin, and a preferred thrombin inhibitor is N-(2-naphthylsulfonylglycyl)-D,L-amidinophenylalaninpiperidide.