Tail-suspension of rats has been shown to cause loss of bone mass similar to that experienced by humans in microgravity. We have applied tail-suspension to mice to characterize bone, nervous system and muscle changes that occur and evaluate the use of magnetic fields to obviate these changes. Results have shown that femurs and tibiae of tail-suspended mice undergo significant decreases in dry weight, stiffness and strength. Immersion of mice in specific oscillating magnetic fields can reduce or eliminate these degenerative changes. Results have also shown that tail-suspended animals undergo changes in spinal cord function similar to changes previously observed in animals with damaged sciatic nerves. These changes include decreases in the uptake of GABA (an inhibitory neurotransmitter) into a purified fraction of synaptic nerve endings and changes in electrical responses recorded in an isolated spinal cord preparation. Finally, muscles undergo significant degeneration which may be related to spinal cord alterations. It remains to be established whether oscillating magnetic fields may be effective in preventing microgravity-induced changes.