The objective of this investigation was to evaluate the efficacy of fluid and salt supplementation in preventing the development of osteopenia in 150 Wistar male rats (370-390 g) after exposure to 90-days of hypokinesia. They were divided into three equal groups: 1st placed under ordinary vivarium conditions (vivarium control animals); 2nd subjected to hypokinesia (unsupplemented hypokinetic animals, HK); and 3rd submitted again to HK and daily supplemented with water (5 ml/100 g b.w.) and NaCl at 0.9 g % (3 ml/100 g b.w.) orally administered (supplemented hypokinetic animals). The hypokinetic effect was carried out by keeping the rats in small individual wood cages which restricted all their movements without hindering feed and water intake. Determination was made of weight and volume of their entire bone, head and distal epiphysis, as well as density, ash and mineral content. Thickness of the cortical layer and width of the bone marrow canal were measured on frontal and lateral x-ray projections. Histological transverse sections of the femoral diaphysis were prepared from the femoral bone fragments. The concentrations of calcium, phosphorus and creatinine in serum were also measured. The results obtained indicate that the daily administration of fluid and salt supplementation inhibited the progressive development of osteopenia in rats subjected to prolonged restriction of motor activity.