In order to investigate the effects of Kaejibokryungwhan, Sobokchugeotang and Dohongsamultang on mesangial cell proliferation and fibronectin synthesis, laboratory study was performed. The results are summarized as follows; 1. Mesangial cell proliferation was significantly decreased in the Kaejibokryungwhan group and the Dohongsamultang group compared with the Control group. In the Sobokchugeotang group, the mesangia1 cell proliferation activity was lesser than Control group, but it was statistically non-significant. In Kaejibokryungwhan group, the Sobokchugeotang group and Dohongsamultang group, mesangial cell proliferation was significantly decreased compared with the Hydrocortisone group 2. In the group, which contained fetal bovine serum, fibronectin synthesis was decreased in the Kaejibokryungwhan group, the Sobokchugeotang group and Dohongsamultang group compared with Control group, but the difference was statistically non-significant. In Kaejibokryungwhan group, Sobokchugeotang group and Dohongsamultang group, fibronectin was less decreased compared with that of Hydrocortisone group. 3. In the group, which contained fetal bovine serum, fibronectin synthesis was significantly decreased in Kaejibokryungwhan group and Sobokchugeotang group than those of Control group. In Dohongsamultang group, the fibronectin synthesis was decreased than Control group, but the difference was statistically non-significant. In Sobokchugeotang group, the fibronectin synthesis was decreased than Hydrocortisone group, but it was statistically non-significant. According to the above results, the mesangial cell proliferation and fibronectin systhesis could be reduced by Kaejibokryungwhan group significantly.