In order to investigate whether serum Cu, Zn and Cu/Zn ratio are the useful indicater for the diagnosis of cancer. serum Cu and Zn levels were determined from 35 normal subjects and 33 stomach cancer patients by Atomic absorption spectrophotometer. The following results are obtained : Serum copper levels of stomach cancer patients were significantly increased than the those of the normal controls. whereas serum Zn levels significantly decreased than those of the normal contros(P<0.01) Therefore the copper to zinc ratio revealed a significant in the serum Cu and Zn levels. The serum protein and albumin levels were significantly lower in cancer patients(P<0.01) And the correlation analysis indicated that there was no significant correlation between serum Cu/Zn ratio and protein or albumin. These data suggest that the serum Cu. Zn and Cu/Zn ratio may be used as a diagnostic test in stomach cancer patients.