Magnesium (Mg(++)) therapy has been shown to be neuroprotective and to facilitate recovery of motor and sensorimotor function in a variety of animal models of traumatic brain injury. However, few studies have investigated the efficacy of Mg(++) therapy on cognitive impairments following injury. The present study evaluated the ability of magnesium chloride (MgCl(2)) to facilitate recovery of function following bilateral anterior medial cortex lesions (bAMC). Rats received electrolytic bAMC lesions or sham surgery and were then treated with 1 mmol/kg, i.p. MgCl(2), 2 mmol/kg, i.p. MgCl(2), or 1.0 ml/kg, i.p. 0.9% saline. Drug treatment was administered 15 min following injury with subsequent injections administered at 24 and 72 h. Rats were tested on a battery of behavioral tests that measured both cognitive (reference and working memory in the Morris Water Maze (MWM) and spatial delayed matching-to-sample (DMTS)) and sensorimotor performance (bilateral tactile adhesive removal). The results indicated that bAMC lesions produced significant cognitive impairments in reference memory and working memory in the MWM, DMTS and sensorimotor impairments compared to shams. Mg(++) therapy exhibited a dose-dependent effect in facilitating recovery of function. Administration of 2mmol of MgCl(2) significantly improved performance on the bilateral adhesive tactile removal test, DMTS and working memory tests. The 1 mmol dose of MgCl(2) reduced the initial deficit on the tactile adhesive removal test and reduced the working memory impairment on the second day of testing. These results suggest Mg(++) therapy improves cognitive performance following injury in a dose-dependent manner.