Subtotal nephrectomy was produced in male Wistar rats and the evolution of arterial pressure, water distribution and electrolytic composition of muscle and arterial tissue were studied. Also, the modifications produced by a chronic administration of saline load were evaluated. The incidence of hypertension is higher in the group that received saline load but the levels of the blood pressure were similar in both groups of hypertensive animals. The total water is increased in all the groups, except at the fourth week in the animals that did not receive saline load, in which it was decreased. The extracellular space is augmented in all groups and the plasma volume increased in the early phases of the experimental period with exception of the normotensive rats without saline load. No alterations were observed in the electrolytic muscle content, and the total water and potassium and chloride content of the arterial tissues was increased without modifications in the sodium content. The possible relationship of these alterations with the development of hypertension are discussed.