To demonstrate efficacy and characterize the dose response relationship of PD 0200390 on subjective wake after sleep onset in subjects with primary insomnia.

Inclusion Criteria:

• 3 month history of primary insomnia;
• 18 to 64 years
• For the last 3 months-regularly awake unrefreshed and unrestored
• Difficulty initiating and maintaining sleep for at least 3 nights/week for the past month (difficulty falling asleep, difficulty staying asleep, early awakening)

Exclusion Criteria:

• Any history of an Axis 1 psychiatric diagnosis;
• History or presence of any breathing related sleep disorder;
• History or presence of any medical or neurological condition that could interfere with sleep
• Use of alcohol as a sleep aid or more than 2 standard drinks consumed per day or more than 14 consumed per week