The purpose of this study was to determine the effects of 4 months of exercise training (ET) on cardiorespiratory function and endurance, blood pressure, muscle strength, hematology, blood lipids, and renal function in individuals with chronic renal failure (CRF) who were not yet on dialysis. Sixteen subjects were recruited to volunteer for participation in this study, but only eight completed all study phases. Subjects were first evaluated before and after a 2-month baseline (BL1 and BL2), after 4 months of ET, and again after 2 months of detraining (DT). ET did not change hematology, blood lipids, or echocardiographic measurements of left ventricular function and mass. Resting systolic and diastolic blood pressures decreased significantly from BL after the ET (146 +/- 15.7/87 +/- 9 mm Hg to 124 +/- 17.5/78 +/- 9.5 mm Hg; P < 0.02), and then increased significantly after DT (139 +/- 14.7 mm Hg and 87 +/- 9.9 mm Hg; P < 0.01). Peak oxygen consumption (pVO2) changed significantly during the study (1.3 +/- 0.3 L/min, 1.5 +/- 0.3 L/min, and 1.4 +/- 0.3 L/min for BL2, ET, and DT, respectively; P < 0.02), as did the VO2 at the ventilatory threshold (0.65 +/- 0.18 L/min, 0.92 +/- 0.19 L/min, and 0.68 +/- 0.23 L/min for BL2, ET, and DT, respectively; P < 0.01). Knee flexion peak torque increased after ET (43.4 +/- 25.6 Nm to 51.0 +/- 30.5 Nm; P < 0.02). GFR, as measured by creatinine clearance, continued to deteriorate during the course of the study (25.3 +/- 12.0 mL/min, 21.8 +/- 13.2 mL/min, and 21.8 +/- 13.2 mL/min for BL2, ET, and DT, respectively; P < 0.001). Individuals with predialysis CRF who undergo ET improve in functional aerobic capacity, muscular strength, and blood pressure.