The effects of several forms of plasminogen on the state of actin cytoskeleton of human platelets were studied. A ratio between various actin pools, which were detected by immunoblotting, was taken as indicator of platelet cytoskeleton reorganization. It was revealed that intact platelets contain globular (G) actin and membrane cortex (MC) actin in amounts that are 56 and 40% of filamentous (F) actin level, respectively. In both thrombin- and collagen-activated platelets, actin is almost entirely presented in F-form. Incubation of resting platelets with Lys-plasminogen causes elevation of MC-actin level up to 79% in respect to F-form content. In addition, Lys-plasminogen inhibits reorganization of actin cytoskeleton typical for activated platelets. In contrast to Lys-form, Glu-plasminogen affects neither platelet aggregation nor redistribution of actin pools. Thus, these data indicate that cytoskeletal structures of platelets are involved in realization of anti-aggregating effects of Lys-plasminogen.