To investigate the anti-complementary and cytotoxic effects of oriental prescription, Kuseonwangdogo, on the proliferation of preadipocyte 3T3- L1 cells, we examined biological effects of Kuseonwangdogo. The results obtained were as follows. 1. After 14 days, the body weight of rats treated with Kuseonwangdogo decreased more than that in the control group (p<0.05). However, the weights of liver, spleen and kidney were unchanged. In serum biochemical test, we examined the level of glucose (GLU) and glutamic pyruvic transaminase (GPT). The levels of GOT and CHOL in serum were decreased remarkably by the administration of Kuseonwangdogo (p<0.05). The haematological examination of the tested group showed significant increment of white blood cells (WBC), hemoglobin concentration (HGB), mean corpuscular hemoglobin (MCH) and monocyte (MO). 2. The effect of Kuseonwangdogo on the proliferation of 3T3-L1 cells was tested by the sulforhodamin B(SRB) assay. The high concentration ($100{mu}l;and;200{mu}l$) of extracts inhibited the proliferation of 3T3- L1 cells. The p-value was <0.01, respectively. 3. The extract of Kuseonwangdogo showed a potent anti -complementary activity. It was suggested that the active principle may be a kind of polysaccharide molecule. 4. The cytotoxic effects of Kuseonwang dogo and its composing herbs in human liver cells (WRL68) and monkey kidney cells (Vero) were examined by the SRB and 3- (4,5- Dimethylthiazol-2-yl) -2,5 diphenyl-2H- tetrazolium bromide (MTT) assay. Cytotoxic effects were not observed.