To evaluate the effects of fluoride on the kidney and the liver of ICR-derived glomerulonephritis (ICGN) mice by using laboratory tests and pathological examinations, fluoride was administered to the ICGN mice at 0, 25, 50, 100, and 150 ppm in drinking water for 4 weeks and to the ICR mice, which have normal kidney function at 0 and 150 ppm. The BUN, creatinine, GOT, and GPT in the serum of each mouse were determined. When a mouse died, the sample from the day closest to the death was assigned for the mean. Pathological changes in the kidney were examined after PAS (periodic acid-Schiff) staining. All of the ICGN mice in the 150 ppm group and one of seven in the 100 ppm group died before the end of week 4, but no ICR mice died. For ICGN mice, the mean value of body weight in the 150 ppm group was significantly lower than those in 0 ppm group and other fluoride-administered groups. The mean values of relative liver and kidney weights in the 100 and 150 ppm groups were significantly lower than those in the control. The mean values of BUN, creatinine, and GPT in the 150 ppm group were significantly higher than those in the control. The thickness of the glomerular capillary wall and the increased mesangial matrix in the kidney were prominent in the fluoride-administered ICGN mice. These results suggested that fluoride severely exacerbated glomerulonephritis and tublar-intestitial changes in ICGN mice.