Current changing epidemiological pattern in the Western Pacific strongly suggests a contribution of the environmental factors to the pathogenetic process of amyotrophic lateral sclerosis (ALS). As a reflection of excess metals and a deficiency of minerals in soil and water samples in these foci, this study was designed experimentally to evaluate the concentration of calcium (Ca), magnesium (Mg) and aluminum (Al) in the bones of rats fed unbalanced mineral diets. Twenty-eight male Wistar rats, weighing 200 g, were fed either a standard diet, a low Ca diet, a low Ca-Mg diet, or a low Ca-Mg diet with high Al for 90 days. The composition of the diet/100 g consists of Ca 1250 mg, Mg 300 mg, Al 10 mg, Zn 4 mg in the standard diet; Ca 3 mg and Mg 2 mg in the low Ca-Mg diet; and Al 194 mg in the high Al diet, Al supplied as Al lactate. Ca, Mg and Al concentrations were determined by using inductively coupled plasma emission spectrometry (ICP) for bone and atomic absorption spectrometry for serum. Serum Ca levels in the groups fed unbalanced mineral diets were lower than those in the group fed standard diet. Serum Mg levels were markedly decreased in the groups fed low Ca-Mg diet and low Ca-Mg plus high Al diet, compared with those in the groups fed standard diet and low Ca diet.(ABSTRACT TRUNCATED AT 250 WORDS)