Since the reduction of calcium (Ca) intake leads Ca and magnesium (Mg) to mobilize from their bone pool and to deposit Ca in the soft tissues, especially in the central nervous system (CNS) tissues, the effects of 4-(o-benzylphenoxy)-N-methylbutylamine hydrochloride (bifemelane) on the deposition of Ca and Mg in the CNS tissues, heart, liver, kidney, muscle, abdominal aorta and bones were studied in rats maintained on low-Ca diets. Thirty-two male, 7-week-old Wistar rats, randomly divided into four groups, each consisting of 8 rats, were maintained for 90 days on the following diets: (A) standard, (B) standard with bifemelane (10 mg/100 g diet), (C) low-Ca, and (D) low-Ca with bifemelane (10 mg/100 g diet). Neither the A-B groups' nor the C-D groups' blood chemistry changed. However, Mg concentration in the cerebellum showed higher values in the B group than in the A group (p less than 0.05). And Mg concentration in pons, cerebellum, spinal cord, heart, liver and femur of the D group increased more than that of the C group (p less than 0.05-0.01), as determined by inductively coupled plasma emission spectrometry (ICP). On the other hand, Ca concentration in the liver was less in the D group than that of the C group (p less than 0.05). In general bifemelane had a tendency to decrease Ca deposition in the CNS and soft tissues of B and D groups. Bifemelane may possibly participate in activating the cerebral metabolism and in keeping an adequate Mg level in the CNS and soft tissues.(ABSTRACT TRUNCATED AT 250 WORDS)