Blood samples were taken from 7 healthy subjects (6 males: 28-59 years old, 1 female: 27 years old) before and after taking Nattokinase 4000FU to measure platelet aggregation capacity. Collagen and ADP were used as aggregation attractants. The results have showed that platelet aggregation inhibition peaked 6 hours after ingestion of Nattokinase in most subjects, indicating a strong inhibition of platelet aggregation.