The present study examined the effects of intermittent hypobaric hypoxic exercise over a period of four weeks on cardiovascular adaptations. Twenty-four healthy male adults (age, 24 ± 3 yrs) who were matched for physical fitness levels were randomized into two groups, and was adjusted to be either normobaric normoxic (N; n = 12) or hypobaric hypoxic (H; n = 12). Both groups performed aquatic activities at an intensity of about 50% VO_2max for 30min/session, four days per week for four weeks in a pool within a chamber where the atmospheric pressure can be regulated. The H group exercised under hypobaric conditions corresponding to 2,000m above sea level, and were exposed for a total of 2.5h/session. Before and after experimental period, VO_2max and cardiovascular responses such as heart rate (HR), stroke volume (SV), cardiac output (CO), as well as systolic (SBP), diastolic (DBP), and mean blood pressure (MBP) were measured during cycling on an ergometer at an intensity of 50% VO_2max. Flowmediated vasodilation (FMD) was also evaluated by measuring changes in the diameter of the popliteal artery between rest and during reactive hyperemia. The VO_2max was not significantly changed after the four-week exercise period in both groups and changes in cardiovascular responses during moderate exercise were not evident in the N group. On the other hand, SV and CO were significantly increased (P＜0.05) in the H group, whereas DBP and MBP as well as the calculated TPR (MBP/CO) were significantly decreased (P＜0.05 for all). The FMD was significantly increased only in the H group (P＜0.05). These findings indicated that exercise under hypobaric hypoxic conditions could induce more beneficial cardiovascular adaptations in healthy male adults such as reductions in TPR and BP with an increase in FMD compared with exercise under normal conditions.