Postural changes in 1-G environment induce well documented haemodynamic changes. On going from Earth's 1-G environment to the microgravity of space a marked cephalic blood volume shift occurs in humans with a subsequent loss of 2-3 L of fluid determined by diuresis and decreased fluid intake. Moreover, a number of transient changes in serum concentrations of sodium, potassium and calium have been observed in astronauts during spaceflight. It is conceivable that changes in the fluid status, and reduced muscle activities, which are changed by the microgravity environment, would also result in redistribution of some trace elements, such as zinc, copper and manganese. In particular, zinc metabolism, directly involved in many physiological processes, can be altered by a wide variety of factors including stress, rest, exercise, hormones and diet. Some of the microgravity-induced responses in space can be simulated in humans by using the posture of head-down tilt, and in rat by using the posture of hindlimb suspension. The aim of the present study was to investigate the effects of hindlimb suspension for 3-14 days on sodium, potassium and zinc content in various rat tissues including blood, muscle, brain, eye and nose's skin.