The purpose of this study is to determine whether a compound known as EVT 201 is effective in treating people diagnosed with primary insomnia ( difficulty sleeping with no other significant contributing factor, such as depression).

Inclusion Criteria:

• must have a diagnosis of primary insomnia
• over the last three months, must have a normal bedtime of between 9 pm and 1 am and a time in bed of at least 7 hours
• must be able to attend the Sleep Center for two consecutive nights on four occasions over a two month period
• must be willing and able to complete a sleep diary and questionnaires

Exclusion Criteria:

• must not have a clinically significant or unstable medical condition that may interfere with sleep
• must not have a major psychiatric disorder (other than insomnia) such as depression, schizophrenia, bipolar disorder
• must not be currently using any medication know to affect sleep e.g. hypnotics, anxiolytics,antidepressants, antihistamines, anticonvulsants
• must not intentionally nap 3 (or more) times per week
• must not smoke more than 10 cigarettes per day and /or be able not to smoke without distress or discomfort for the duration of visits to the sleep laboratory ( i.e. approximately 12 hours)