The effects of contention stress on renal functions were evaluated on two rats groups: control group and immobilized group (4 hours/day, for 10 days in special contention cages). Both groups had access either to 0.5% or 1.5 % saline solution. The sodium intake, water intake, the sodium and potassium renal excretion, Na/K ratio, water renal excretion were evaluated. Sodium intake in immobilized group rats was lower than in control rats during all observed periods. There was a significant decrease of the sodium and potassium renal excretion in the 10th day vs the 1st day. The Na/K ratio was not modified. The urine volume was reduced in the stressed animals. This suggests that the contention stress reduces the appetite for Na as a result of kidney inability to excrete this ion.