Renewed interest has arisen in the use of thromboelastography/thromboelastometry in evaluating coagulation kinetics. The test medium, type of activator, and its concentration may influence the interpretation of coagulation kinetics. This study aimed to investigate methodologic influences of activator and test medium on thromboelastometric parameters of coagulation kinetics. Dynamic clot formation was evaluated by thromboelastometry using whole blood (WB), platelet-rich plasma, or platelet-poor plasma employing different concentrations of extrinsic (tissue factor) and contact activator (synthasil) and with variable concentrations of phospholipids. Plasma samples displayed prolonged clot initiation and enhanced clot propagation compared with WB. Clot firmness was markedly reduced in platelet-poor plasma as compared with platelet-rich plasma and WB. Increasing concentration of activator shortened the clot initiation and increased the velocity of clot propagation, whereas terminal clot firmness remained unaffected. Platelets accelerated clot propagation and raised clot firmness. Phospholipids shortened the time of clot initiation and increased velocity of propagation, while clot firmness remained unchanged. Our results demonstrate that evaluation of coagulation kinetics using thromboelastometry varies according to the composition of the test medium, type, and concentration of activator, as well as the presence and concentration of phospholipids in the test reagent.