The effect of the structure of a mixture of industrially produced iron and iron oxide on the decomposition of trichloroethylene (TCE) was investigated by gas chromatography, scanning electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray analysis, X-ray diffractometry, and 57 Fe-Mössbauer spectroscopy. The concentration of 10 mg L -1 TCE aqueous solution decreased to 0.41, 0.52, 0.26, and 0.09 mg L -1 when stirred for 7 days with iron-iron oxide mixtures having mass ratios of 2:8, 3:7, 4:6, and 5:5, respectively. The Mössbauer spectra of the mixtures after leaching were composed of two sextets with respective isomer shifts (d) and internal magnetic fields (H) of 0.29 ±0.01 mm s -1 and 48.8 ±0.1 T, and 0.64 ±0.01 mm s -1 and 45.5 ±0.1 T, attributed to the Fe 3? species in tetrahedral (T d ) and the Fe 2? and Fe 3? mixed species (Fe 2.5? ) in octahedral (O h ) sites, respectively. Mössbauer spectra of a 3:7 mass ratio iron-iron oxide mixture showed a gradual decrease in the absorption area (A) of zero valent iron (Fe 0 ) from 40.6. to 12.6, 13.2, 3.8 2.8, and 1.0 ±0.5 % and an increase in A of Fe 3 O 4 from 31.8 to 59.4, 71.4, 93.2, 95.6, and 98.0 ±0.5 % after leaching with 10 mg L -1 TCE aqueous solution for 1, 2, 3, 7, and 10 days, respectively. Consistent values of the first-order rate constant were calculated as 0.32 day -1 for Fe 0 oxidation, 0.34 day -1 for Fe 3 O 4 production, and 0.30 day -1 for TCE decomposition, which indicates that the oxidation of Fe 0 was the rate-controlling factor for Fe 3 O 4 production and TCE decomposition. It is concluded from the experimental results that an iron-iron oxide mixture is very effective for the decomposition of TCE.