Hierarchical porous alpha-Fe2O3/TiO2 nanorod@core-shell microspheres were synthesized by a facile one-step hydrothermal approach without templates or surfactants. The as-obtained alpha-Fe2O3/TiO2 nanorod@core-shell microspheres had an average diameter of 3.5 mu m. Porous nanorods, with an average length of 1.5 mu m, were randomly grown on the core-shell microsphere surfaces. The morphology, microstructure, and composition of the alpha-Fe2O3/TiO2 heterostructures were characterized by various analytical techniques. Changes in the morphology and composition of the microspheres had an effect on the final gas sensing performance. Gas sensors based on the porous nanorod@core-shell alpha-Fe2O3/TiO2 microspheres exhibited an excellent gas-sensing performance, with markedly enhanced responses in comparison with the pristine alpha-Fe2O3 sensor. The response of the porous nanorod@core-shell alpha-Fe2O3/TiO2 microspheres to 20 ppm acetone was approximately 34, which was 2.7 times higher than that of pure alpha-Fe2O3 at 220 degrees C. Furthermore, the sensor could be easily recovered to its initial state following a short exposure to fresh air. The remarkably enhanced acetone-sensing performance was attributed to the unique porous nanorod@core-shell microsphere morphology, the strong interfacial interaction between TiO2 and alpha-Fe2O3, and the presence of alpha-Fe2O3/TiO2 heterojunctions. Thus, the prepared porous nanorod@core-shell alpha-Fe2O3/TiO2 microspheres sensors showed an outstanding performance in acetone detection.