Biomedical inorganic chemistry is an important new area of chemistry. Gold complexes are clinical use for the treatment of solid tumors. Treatment with gold compounds, especially gold (III) may be accompanied by many side effects due to its unsuitability. In this work, a new gold (III) complex with N,N'-di(3- methylbenzlediene)dithiooxamide was used. It is a polydentate ligand containing a biologically important (imine) group. This new complex classified with new family of transition metal complexes conjugated with Schiff-bases possessing potential antitumor agent. The structural formula of the new complex has been suggested to be square planar, using the usual instrumental techniques. It was found that gold coordinated sulfur atoms of the legend. DMSO and mixture of DMF-Isopropanol (1 part 9 part) were found to be the best solvents for the complex. The antitumor effect of the gold complex was studied against two cell lines, i.e. Plasmacytoma and hepatocellular, in different incubation periods (24,48,72 and96) hrs. compared with study of its effects on normal cells (mouse embryo fibroblast). The study of its effect on (mouse embryo fibroblast) has been done at two incubation periods (7 and 10) days done. The LD50 was determined and found to be (05 mg/Kg (4.2 mg/ml).