The purpose of this study is to determine whether a compound known as EVT 201 is effective in treating elderly patients diagnosed with primary insomnia who also have moderate daytime sleepiness.

Inclusion Criteria:

• Diagnosis of primary insomnia according to DSM-IV
• Over the last three months for at least 5 nights per week, must have a normal bedtime of between 9 pm and 1 am and a time in bed of at least 7 hours
• A history of sleepiness, tiredness or unintentional napping during the daytime attributed to to poor sleep at night
• Able to attend the Sleep Center for five nights (two consecutive nights on two occasions and one night on one occasion)over a five week period
• Willing and able to complete a sleep diary and questionnaires

Exclusion Criteria:

• Clinically significant or unstable medical condition that may interfere with sleep
• Major psychiatric disorders (other than insomnia) such as depression, schizophrenia, bipolar disorder
• History of myocardial infarction, cardiac failure or clinically significant dysrhythmias in the previous 2 years or clinically significant ECG abnormalities at screening
• History of substance abuse
• Disorders that interfere with drug pharmacokinetics
• History of cancer, except basal cell carcinoma
• Use of hypnotics, anxiolytics, antidepressants, anticonvulsants, over-the-counter sleep aids, histamine-1 receptor antagonists (except for loratadine and fexofenadine), beta-adrenergic blockers (except for atenolol), respiratory stimulants and decongestants, systemic steroids, narcotic analgesics, any other compound which might impact sleep-wake function, or medication used for the treatment of Parkinson's disease such as dopamine agonists and L-dopa (e.g., Sinemet, Madopar or Requip)
• Use of hypnotics within the 2 weeks preceding the Screening Period or within five half-lives of the medication, whichever is longer
• Consuming ≥ 350 mg per day of xanthine-containing food or beverages
• Smoking ≥ 10 cigarettes per day and/or unable to refrain from smoking without distress or discomfort for the duration of visits to the sleep laboratory (i.e.≥ 20 hours)
• Body mass index > 34 kg/m2;
• Performing night work or rotating shift work during the past month
• Traveling across > 3 time zones in the past 2 weeks
• Participation in another trial of an investigational product or device within the previous 30 days
• Known allergy or sensitivity to benzodiazepines