Fibrinolysis reduces the risk of a cardiovascular advent. A diminished fibrinolytic activity is associated with adverse cardiovascular events that may be related to exertion and resting fibrinolysis is affected by exposure to extreme hot and cold temperatures. However, it is unknown if ambient temperature impacts the fibrinolytic response to exercise. Purpose. The purpose of this study was to assess the fibrinolytic response to an acute bout of aerobic exercise bout during exposure to both hot and cold temperatures and to compare those responses to exercise in ambient conditions. Methods. Fifteen apparently healthy males (25.3 ± 4.3 years) participated in this study. Over 3 separate testing sessions each subject performed a V02i test on an electronically-braked cycle ergometer at 3 different temperatures (20°C, 5-8°C, 30°C), with a minimum 7 day interval between each session. Blood samples were obtained following a 15 minute baseline period of seated rest and within two minutes of post exercise. Plasma concentrations of the 2 primary mediators of fibrinolytic potential, t-PA and PAM, were assessed at baseline and immediately post exercise. Results. In response to the exercise test, t-PA activity increased (normal 0.7 - 2.7 IUlml'1, hot 0.7 – 2.61U/ml-1, cold 0.9 – 2.6 IU/ml'1) and (normal 13.7 – 11.8 IU/m ' , hot 14.4 -- 9.5 IU/ml'', cold 9.9 -- 7.4 IU/ml'1). No main effect of temperature for t-PA activity and PAI-1 activity was found and no significant temperature x time interaction was observed for either fibrinolytic markers. Conclusions. Given the relationship between fibrinolytic activity, temperature and the physiological changes that occur with temperature favor cardiovascular events. However no fibrinolytic link was associated with increased exercise and temperature risk of cardiovascular events.