Platelets clearly play an important role in inflammatory responses. In this study, we aimed to evaluate the relationship between aging and platelet activation. A total number of 799 persons (383 males and 416 females), who were apparently healthy and aged more than 20 years were recruited by a health promotion center in a community-based hospital in Seoul, Korea. We collected material data about their medical history and health behavior. Platelet parameters including mean platelet component (MPC), mean platelet volume (MPV), and platelet component distribution width (PCDW) were determined within 1 hour after blood collection using the ADVIA 120 automated hematology analyzer. The MPC of the women ($27.2{pm}1.2$) was significantly love. than that of the men ($27.5{pm}1.3$). The MPC of all participants was found to decrease with increasing age (P<0.01). Study participants in their twenties had the highest MPC ($27.7{pm}1.1$), followed by those in their thirties ($27.6{pm}1.1$), forties ($27.4{pm}1.3$), fifties ($27.2{pm}1.3$), sixties ($27.2{pm}1.2$) and seventies ($27.1{pm}1.2$). Multiple regression analysis showed that aging and gender were related with MPC after adjusting for confounding factors, including age, gender, smoking habit, hypertension, diabetes, body mass index and total cholesterol level. The this study shows that aging is related to platelet activation. Future research will need to determine the implications of increased platelet activation with aging, especially regarding the increased incidence of cardiovascular diseases and related mortalities that occur in older age groups.