Rh-1 is a humanoid robot under development at the University Carlos III of Madrid. Along with other interaction types, the robot is capable of recognizing voice commands. This article describes the sound localization system that has been added recently. It is independent of the voice recognition system and uses the information from several microphones attached to the robot's head that is further processed in order to estimate the sound source direction. Results are presented and discussed and the ideas how to improve the performance are suggested. © 2007 World Scientific Publishing Co. Pte. Ltd.