The aim of this study was to assess the effects of aerobic exercise on resting and 24-hour blood pressure (BP), left ventricular mass (LVM), plasma fibrinogen and factor VII (FVII). For this purpose 14 sedentary subjects with untreated diastolic BP between 90 and 104 mm Hg completed a 12-week supervised exercise program. At the end of this period, 8 subjects resumed a sedentary life-style and were reexamined 2 months later (detraining). Baseline, posttraining and postdetraining examinations included resting BP assessment, ambulatory BP monitoring, cardiopulmonary stress test, echocardiography and measurements of plasma fibrinogen and FVII. Exercise-mediated increase in aerobic fitness (VO2 max + 24%) was associated with a significant reduction in resting systolic and diastolic BP (p < 0.01), mean systolic and diastolic 24-hour BP (p < 0.001) and LVM index. As for the coagulation parameters only the concentration of fibrinogen significantly decreased (p < 0.01) whereas FVII remained unchanged. The 8 subjects that resumed a sedentary life-style were reexamined 2 months later: their resting BP, 24-hour BP and fibrinogen concentration returned to baseline values; only the effect on LVM was conserved. Our study underlines the usefulness and safety of regular physical exercise in mild hypertension. Most of the patients (11 of 14) had their BP normalized and a significant reduction in LVM and fibrinogen concentration was observed, leading to an overall improvement in coronary risk profile.