The Thrombin Activatable Fibrinolysis Inhibitor (TAFI) is a recently described inhibitor of fibrinolysis. The physiological variations of plasma TAFI antigen are not well known. We studied TAFI antigen values in healthy populations with a commercially available kit from Milan Analytica (Switzerland). Broad range of TAFI antigen values (from 41% to 259%) was found in a population of 249 healthy individuals. Gender as well as pregnancy did not influence mean values of TAFI antigen. There was a positive correlation between TAFI antigen and age in female (r = 0.28; p <0.05) but not in male populations. Mean TAFI antigen value of a black African male group [mean +/- SD (range): 87 +/- 23 (39-144%)] was significantly lower than the one of age matched Caucasian men [114 +/- 34 (52-259%)] (p <0.0001). TAFI antigen values were very stable within individuals, they did not significantly vary on day time or at several months period. Thus, in contrast to large inter-individual variations, TAFI antigen levels are quite stable within individuals.