Current epidemiological surveys in the Western Pacific (Guam, and Kii Peninsula and West New Guinea) have suggested that low calcium (Ca), magnesium (Mg) and high aluminum (Al) and manganese (Mn) in river, soil and drinking water may be implicated in the pathogenetic process of foci of amyotrophic lateral sclerosis (ALS) and parkinsonism-dementia (PD). The condition of unbalanced minerals was experimentally mimicked in this study using rats. Male Wistar rats, weighing 200 g, were maintained for 60 days on the following diets: (A) standard diet, (B) low Ca diet, (C) low Ca diet plus high Al. Magnesium concentrations were determined in spinal cord and trabecular bone using inductively coupled plasma emission spectrometry (ICP). In the experimental group maintained on a low Ca, high Al diet, magnesium concentration of the spinal cord was lower than the group fed a standard diet. Also, magnesium concentration of lumbar vertebra showed lower values in the experimental group fed a low Ca, high Al diet than did those on a standard diet or low Ca diet without supplemental aluminum. Our data indicate that low Ca, high Al diet influences Mg concentration in bone and central nervous system (CNS) tissues and that a low Ca, high Al diet diminishes Mg in bone and CNS tissues, thereby inducing loss of calcification in bone and degeneration of CNS tissue due to alteration of the normal biological effects of Mg.