Using FeSO4 x 7H2O and H2O2 as raw materials, a facile route to selective synthesis of alpha-FeOOH and alpha-Fe2O3 nanorods was developed by adjusting the reaction temperature in hydrothermal synthesis. Without undergoing calcinations, the obtained alpha-FeOOH nanorods (at 150 degrees C) and alpha-Fe2O3 nanorods (at 200 degrees C) possess high morphological yield (> 95%). The influences of synthesis conditions such as H2O2, hydrothermal temperature and hydrothermal time were investigated. The formation process of alpha-FeOOH and alpha-Fe2O3 nanorods was discussed in detail, and a possible temperature-controlled selective synthesis mechanism was proposed.