(1) Polyenes aggregate platelets. The aggregation power diminishes in the following order: filipin > nystatin > etruscomycin∼pimaricin. (2) In the case of filipin, aggregation is probably caused by damage to platelets resulting in a release of platelet contents, which subsequent aggregates the remaining platelets. (3) Filipin-induced aggregation can be partially inhibited by adenosine and is Ca++ pimaricin. (6) The uptake of serotonin by platelets is diminshed by polyenes. Leakage of 86Rb from preloaded platelets increases upon addition of polyene