The purpose of this thesis is to determine what effects a dietary magnesium deficiency has on the discriminative avoidance behavior of rats. Three experiments were conducted. Experiment I compared two groups to determine the effects of magnesium deficiency on bar-press discriminative avoidance behavior. The results of Experiment l clearly illustrated that rats fed n diet deficient in magnesium began to lose their discriminative avoidance behavior after approximately five days with a steady decrease in performance over the remaining five days. Experiment II used a single subject design in an attempt to replicate Experiment I and to determine whether or not the magnesium deficiency effect could be reversed. Blood samples of serum magnesium for each rat were taken daily. The results confirmed Experiment I. A magnesium deficiency did cause a decrease in the performance of discriminative bar-press avoidance. Two of the four rats responded to the rehabilitation treatment with a corresponding increase in avoidance behavior with an increase in serum magnesium levels. The other two rats did not recover avoidance performance with rehabilitation, but did improve with regard to other behavioral measurements. Experiment III again employed two groups of rats in an attempt to determine the effects of a magnesium deficiency upon acquisition of a discriminative shuttle box avoidance performance. A pilot study to Experiment III showed a clear effect with normal controls displaying statistically more avoidance responses than the experimentals who received subnormal levels of magnesium. The results from Experiment III however showed no statistically significant difference between the controls and experimentals even though there was a statistical difference in serum magnesium concentration.