This 48-week study will compare AVANDAMET vs. Metformin monotherapy for blood glucose control in patients with Type 2 Diabetes Mellitus.

Inclusion Criteria:

• Patients between 18 and 75 years of age with Type 2 Diabetes Mellitus and are currently on metformin monotherapy for glycemic control (100mg daily for at least 3 months prior to screening).
• Patients must have stopped previous treatment with thiazolidinediones or other anti-diabetic agents at least 3 months prior to screening.
• Women must be post-menopausal, surgically sterile or using acceptable contraceptive measures.

Exclusion Criteria:

• Prior history of hepatocellular reaction to or severe edema associated with the use of thiazolidinediones.
• Have a known hypersensitivity to thiazolidinediones or biguanides.
• Currently using insulin or any oral anti-diabetic agent other than metformin.
• History of metabolic acidosis.
• History of substance abuse.
• Have active cancer other than localized squamous or basal cell carcinoma.
• Chronic disease requiring treatment with corticosteroids.
• Other criteria will be evaluated at the screening visit.