BACKGROUND Hemorheological responses to swimming exercise have never been investigated in spontaneously hypertensive rats (SHR). OBJECTIVE We aimed to investigate the effects of moderate intensity swimming exercise followed by detraining on erythrocyte deformability and aggregation in SHR. METHODS SHR and WKY rats were randomized into sedentary, exercised, detrained (5 weeks) and late detrained (10 weeks) groups. Swimming exercise of 60 min, 5 days/week, 10 weeks was applied. Systolic blood pressure (SBP), heart rate, body weights were measured every 2 weeks. Erythrocyte deformability and aggregation were determined by ektacytometry. RESULTS Exercise training reduced SBP in both WKY and SHR rats and decreased erythrocyte aggregation in SHR group. SBP lowering effect of exercise was maintained until a detraining period equal to the duration of the exercise protocol, while 5 weeks of detraining reverted the improvements observed in erythrocyte aggregation of hypertensive rats. Although exercise training did not affect erythrocyte deformability, detraining for 10 weeks decreased RBC deformability in normotensive, but not in hypertensive rats. CONCLUSIONS It can be suggested that, the exercise training applied herein has favorable effects on circulation not only by lowering blood pressure, but also by decreasing erythrocyte aggregation which are reversed after 5 weeks of detraining in SHR.