The objective of our study was: (1) to compare the influence of moderate exercise on circulatory afterresponse in mildly hypertensive (n = 8) and normotensive male subjects (n = 9); (2) to examine the circulatory response to 3-min hyperoxic inactivation of arterial chemoreceptors at rest and during postexercise period in both groups. Hypertensive men (HTS) with a systolic blood pressure (SBP) 148 ؎ 5 mm Hg, diastolic blood pressure (DBP) 92.4 ؎ 4 mm Hg; and normotensive men (NTS), with a SBP 126 ؎ 3 mm Hg, DBP 75.6 ؎ 1.3 mm Hg, were submitted to 20-min of moderate exercise on a cycloergometer (up to the level of 55% of each subject's resting heart rate reserve). Finger arterial BP was recorded continuously with Finapres, impedance reography was used for recording stroke volume, cardiac output and arm blood flow. In HTS a significant decrease in SBP by 14.5 ؎ 3.4 mm Hg, DBP by 8.9 ؎ 1.9