Modafinil (Provigil is a wake-promoting agent that is pharmacologically distinct from CNS stimulants, such as amfetamine, dexamfetamine and methylphenidate. Modafinil is approved for use in the US and certain European countries for use in patients with excessive sleepiness associated with narcolepsy, obstructive sleep apnoea/hypopnoea syndrome (OSA/HS) or shift work sleep disorder (SWSD). Oral modafinil promotes wakefulness in patients with OSA/HS and SWSD. It is an effective adjunctive therapy in patients with residual excessive sleepiness associated with OSA/HS who are receiving nasal continuous positive airway pressure (nCPAP) therapy. In SWSD, the drug improves night-time wakefulness without disrupting daytime sleep. Modafinil is generally well tolerated in patients with OSA/HS or SWSD and has a low abuse potential. Thus, modafinil is a valuable new treatment option for use in patients with excessive sleepiness associated with OSA/HS (as an adjunct to nCPAP) or SWSD.