Modafinil is an agent that is frequently used in the treatment of narcolepsy. More recently it has been used in the treatment of a variety of psychiatric, neurological, and medical illnesses. Due to its ability to improve wakefulness, modafinil has been viewed as a stimulant. Based on the potential for modafinil to become widely used in a variety of syndromes and settings, evidence from preclinical in vitro and in vivo studies, human laboratory studies, and post-marketing experiences examining the potential abuse liability of modafinil were reviewed. Initial evidence suggests that modafinil has limited potential for large-scale abuse.