This larger, definitive study, funded by a National Cancer Research Institute research award, will establish more clearly whether modafinil can improve fatigue in patients with lung cancer. Two hundred and six patients will be recruited from a number of sites across the UK. Half of the patients will take modafinil, and the other half will take a 'dummy' tablet every day for a month. The fatigue levels of the two groups will be compared. Confirmation that modafinil can relieve cancer-related fatigue could have a highly significant impact on the quality of life of the very large number of patients suffering from this common and distressing symptom.