The possible beneficial effect of regular aquatic exercise on cardiorespiratory, renal lipid parameters and oxidative stress status was studied in patients with mild to moderate renal failure. The exercise group did low-intensity aerobic exercise in the pool during a period of 12 weeks, twice a week, with sessions lasting for 30 min. Matched control participants remained sedentary. The results showed that in the exercise group all cardiorespiratory functional parameters improved and resting blood pressure lowered significantly. Proteinuria and cystatin-C were diminished significantly and glomerular filtration rate was enhanced. To evaluate the changes in oxidative stress status in the serum, products of lipid peroxidation (LPO) and serum glutathione values were measured. LPO was reduced significantly and reduced glutathione levels showed significant improvement after the exercise-conditioning programme. In the control group the data either remained the same or worsened in the same period of time. In conclusion, regular water-based exercise has beneficial effects on the cardiorespiratory, renal functional parameters and oxidative stress status in patients with moderate renal failure, and can be used in the complex rehabilitation of chronic renal failure patients, together with blood pressure control, dietary consultation, encouragement and education to prevent physical worsening and to postpone cardiovascular and renal atherosclerotic complications.