This study aimed to investigate the effects of moderate intensity swimming exercise (10 weeks) followed by detraining (for five and 10 weeks) on oxidative stress levels of heart, lung, kidney, and liver tissues and systolic blood pressure (SBP) of spontaneously hypertensive rats (SHR). SHR and control rats were randomized into sedentary, exercised, detrained (5 weeks) and late-detrained (10 weeks) groups. Corresponding sedentary rats were grouped as time 1-2-3. Exercise of 60 min, 5 days/week/10 weeks was applied. Detraining rats underwent the same training protocol and then discontinued training during next 5, 10 weeks. SBP was measured by tail-cuff method. Tissue total oxidant/antioxidant status was measured using a commercial kit and oxidative stress index (OSI) was calculated. Exercise training slightly decreased tissue OSI of SHR and reduced SBP of both groups. Tissue OSI of SHR were higher than WKY and aging resulted in increment of oxidants in groups. detraining yielded time-dependent increments in oxidative stress of all tissues and SBP of both rat groups. Although short-term cessations may be tolerated, our results emphasize the importance of exercising as a way of life for cardiovascular well-being in hypertensives or in individuals who are genetically under risk of hypertension.