The literature on hemostatic processes in swine is sparse and often fragmentary; hence, we conducted our study to characterize age-related changes in selected parameters of primary and secondary hemostasis in 50 growing pigs between day 2 and week 24 of age. We measured platelet count (PLT), mean platelet volume, platelet-to-large cell ratio, prothrombin time, activated partial thromboplastin time (aPTT), thrombin time (TT), and fibrinogen concentration. Among primary hemostasis parameters, PLT underwent the largest fluctuation with the animals' age, ranging from 340 to 730 × 10(9)/L. However, statistical significance was only detected for 4-week-old piglets compared to 18-week-old animals. Of the secondary hemostasis parameters measured, TT and aPTT were the most changeable. Activated partial thromboplastin time displayed a characteristic biphasic course, being relatively short before week 5 of age (17.8-19.9 s) and then becoming much longer (28.7-52.5 s). The aPTTs measured in animals 6 weeks of age and older were statistically different (p < 0.01) from those in younger piglets. The 2 main components of hemostasis, platelet hemostasis and plasma coagulation, did not develop at the same time. It took much longer for secondary hemostasis to stabilize, whereas platelet parameters were stable early in life.