Understanding the intentions of others presumably involves a human analog of the mirror neuron system. A putative marker of such mirror activity is the suppression of electroencephalographic oscillations in the 8-12 Hz range, which, when recorded over somatosensory areas, is associated with motor activity and labeled mu rhythms. We investigated whether mu-suppression can be modulated by attention to another person's intention as expressed by her hand movement toward an object and whether this suppression is distinguished from the suppression of alpha waves that oscillate in the same frequency range and are modulated by attention and cognitive load. Both mu and alpha suppressions were modulated by task difficulty, and not distinctively by intention, reflecting the recruitment of resources needed for task performance. NeuroReport 21:1050-1054 (C) 2010 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.