We investigated the differences in manganese concentration and distribution in the brains of rats administered MnCl2 perorally, intravenously and intraperitoneally for one week. Forty two male Wistar rats were divided into eight groups, designated A to H. Groups A (n = 5) and B (n = 7) were maintained with synthetic diets, with 50 and 1000 mg manganese per kg diets, respectively. Groups C (n = 5), D (n = 5) and E (n = 5) were administered manganese intravenously with dosages of 0.088, 0.88 and 2.2 mg/kg.b.w./day, respectively. Groups F (n = 5), G (n = 5) and H (n = 5) were administered manganese intraperitoneally with dosages of 0.088, 0.88 and 2.2 mg/kg.b.w/day, respectively. Four brain regions (cerebrum, cerebellum, basal ganglia and the remainder) were analyzed by atomic absorption spectrophotometry for manganese. The manganese concentrations in basal ganglia were increased proportionally to the administration dosages in intravenous administration groups (C, D and E). At the highest dosage of manganese administration, manganese concentrations in cerebrum and basal ganglia were higher with intravenous administration of manganese than with intraperitoneal administration. In addition, manganese concentrations were hardly increased in peroral administration groups. Therefore, we suggested that basal ganglia are vulnerable to manganese exposure and that liver and intestine might play the important roles in the reduction of manganese accumulation in the central nervous system.