Modafinil is a central nervous system stimulant approved in Canada for the symptomatic treatment of excessive sleepiness in adult patients with narcolepsy, obstructive sleep apnea, and shift work sleep disorder. Its efficacy has also tested in a number of off-label conditions such as fatigue related to multiple sclerosis (MS) or Parkinson's disease, cocaine addiction, attention deficit disorder, and depression. Modafinil's mechanism of action of promoting wakefulness is not known, but it has a different pharmacologic profile than other stimulants used in sleep disorders, namely methylphenidate or amphetamines. This report will review the safety and efficacy of modafinil in patients with sleep disorders, or fatigue due to MS, in order to inform funding decisions.