MK0952 is a phosphodiesterase type IV (PDE4) inhibitor in development for improvement of cognitive impairment in mild-to-moderate Alzheimer's disease.

Inclusion Criteria:

• Male or females
• Age >/= 55 years, With mild-to-moderate AD, with MMSE between 18 and 26, inclusive, MHIS score </= 4, Global CDR score of 1 or 2
• Who have a reliable informant/caregiver to accompany patient to all clinic visits
• If using a symptomatic AD treatments, patients must be on stable dose for >/= 6 months

Exclusion Criteria:

• Patients must not be living in nursing home or skilled nursing facility
• Patients must not have current evidence and/or history of Crohn's disease, ulcerative colitis, proctitis, GI bleeding, mesenteric arteritis
• Patients must not have current evidence and/or history of poorly-controlled hypertension, clinically significant cardiac arrhythmia, angina, or CHF
• Patients must not have current evidence and/or history of a psychotic disorder or major untreated depressive disorder
• Patients must not have current evidence and/or history of stroke or multiple lacunar infarcts, or neurological or neurodegenerative disorder (other than AD)
• Various concomitant therapy restrictions