Central nervous system (CNS) stimulants are the only class of drug established as being directly effective in relieving fatigue. Traditional stimulants, such as methylphenidate (Ritalin), can cause side-effects such as difficulty sleeping at night and anxiety. Modafinil is a relatively new stimulant with few side-effects. There is increasing evidence that modafinil can reduce fatigue in healthy individuals and patients with chronic, non-cancer conditions. No good quality studies have been published evaluating modafinil in patients with cancer, despite multiple calls for such research to be undertaken.