This study was conducted to investigate the effects of long-term administration of a calcium-channel antagonist (nifedipine) and a β-blocker (acebutolol) on physical fitness in men with mild hypertension. All subjects underwent symptom-limited treadmill stress testing and routine echocardiographic studies. Twenty-two subjects who had either a casual diastolic blood pressure of more than 105mmHg or a left ventricular mass index (LVMI) of 125g/m² or more during follow-up were assigned to receive medical therapy. The other 31 men who did not meet either criterion were continuously followed-up without medication. Among the 22 treated men, the age-adjusted treadmill time (normalized treadmill time, TMTn) significantly decreased before the initiation of medication, while 31 untreated men showed no change in TMTn throughout the study. The 22 treated subjects were subsequently divided into two groups; 13 were given nifedipine and 9 were given acebutolol. All treated subjects were followed-up for more than 3 years. After treatment, the two groups showed similar reductions in blood pressure and LVMI, but a different outcome for TMTn: TMTn increased from 104±8% to 115±16% in subjects given nifedipine (p<0.05) and decreased from 106±12% to 99±10% (p<0.01) in those given acebutolol. Thus, the physical fitness of subjects who required medication significantly deteriorated without medication; their physical fitness improved after treatment with a calcium-channel antagonist and deteriorated after treatment with a β-blocker. (Hypertens Res 1997; 20: 105-111)