Many peritoneal dialysis patients are overhydrated. Overhydration may lead to hypertension and left ventricular hypertrophy, and may be related to inflammation and malnutrition. The presence of overhydration is not always detected by clinical examination. Especially patients with peritoneal ultrafiltration failure and/or negligible residual renal function are prone to overhydration. Treatment consists of a combination of sodium and fluid restriction, in combination with increased peritoneal ultrafiltration and loop diuretics in patients with residual diuresis. Peritoneal ultrafiltration can be enhanced by the use of hypertonic glucose solutions or icodextrin. In some, but not all, studies, residual renal function or diuresis declined with an increase in peritoneal ultrafiltration. At least in a subset of patients, underhydration might have played a role in this phenomenon. We propose to treat overhydration using both clinical criteria and objective techniques such as vena cava echography or bioimpedance measurements.