Effects Of GW679769 On Sleep Onset And Maintenance And Next Day Functioning In Subjects With Primary Insomnia

Inclusion Criteria: * Difficulty going to sleep and/or staying asleep for at least the past 3 months. * Insomnia must result in significant distress or impairment in functioning at home, socially or at work. * Otherwise good health with no significant or unstable medical disorder including psychiatric, neurological, endocrine, heart, lung or gastrointestinal disorders, drug/alcohol abuse, cognitive impairment, cancer or chronic pain conditions such as arthritis. Exclusion Criteria: * History of other sleep disorders such as sleep apnea or restless leg syndrome. * Regular sleep habits, including bedtime between 9 PM and midnight. * No nightshift/rotating shift work, frequent napping or planned travel across \>2 time zones. * Use of nicotine, caffeine and alcoholic products.