In this study, cyanide and thiocyanate levels at liver. spleen, kidney and muscle tissue samples obtained from mice which were given diferent doses sodium nitroprusside (SNP) were investigated. The cyanide and thiocyanate levels in the samples were colorimetrically determined the oxidation of cyanide and thiocyanate by bromine water and coupling of pyridine - benzidine reagents. Absorbances were measured at 532 nm. The cyanide and thiocyanate levels in tissue samples increased after 12 h. and arrived the maximum levels at the different times according to doses.Then the cyanide and thiocyanate ievels in samples decreased the same levels with control groups at 192 h.