With the same forage to the mice, three experiments were done. The control group took water and experimental group took 1% taurine. 1. After the mice were vaccinated with S180 sarcoma, every group was further divided into two groups, one treated with cytoxan (CTX), another one treated with nothing. The survival period, weight of the tumor and the tumor inhibition rate were investigated. The result shows: The survival period of the group fed with taurine was (35.75 +/- 23.7) days longer than that of the control group (18.7 +/- 5.6) days, and the tumor inhibition rate was 42.26%. The mice fed with taurine and treated with CTX survived to 61 days with no death, and no tumor could be seen grossly, so the tumor inhibition rate is 100%. The survival period and weight of the tumor were not different between the CTX treated and control groups. 2. Tumor cell membrane fluidity was observed after the mice were vaccinated with Erlish ascitic tumor. The result shows: in the taurine group, the fluorescence polarization (p) is 0.108 +/- 0.020, the viscosity (eta) is 0.618 +/- 0.140 and in the control group p is 0.139 +/- 0.20, eta is 0.874 +/- 0.150, respectively. Thus the cell membrane fluidity of the taurine group is also obviously better than that of the control group (P < 0.01). 3. The immune functions of the two groups were determined by carbon clearance test and capacity of serum hemolysin. The immune function of the taurine group is also obviously higher than that of control group (P < 0.01). All the results described above show:taurine is functioning for tumor inhibition, and has obvious synergic effect while treated with CTX as chemotherophy. It is considered that the tumor inhibit function of taurine may be related to its effects of immune enhancing and membrane profecting.