Poly(dimethylsiloxane)/iron(III) oxide composite powders were obtained by thermal treatment of polymer-oxide mixtures. The composites present themselves as free-flowing powders, visually indistinguishable from the pure oxide. They are, however, highly hydrophobic and cannot be dispersed in polar solvents. Cylindrical test specimens were obtained by pressing a composite powder and heating it at two different temperatures. Specimens heated at 270 and 300 degrees C present compressive strengths of 1.19 x 10(7) and 1.55 x 10(6) N m(-2), respectively. Scanning electron microscopy of the fracture surfaces reveals the presence of silicone-rich domains, these being larger and more abundant in the specimens heated at 300 degrees C. These domains probably act as stress absorbent-dissipative sites which are responsible for the high compressive strength of the composites.