Many people with type 2 diabetes cannot maintain target blood glucose levels when taking a single oral drug. The purpose of this study is to assess the safety and effectiveness of two doses of vildagliptin, an unapproved drug, when added to metformin in people with type 2 diabetes who are not at target blood glucose levels on metformin alone.

Inclusion Criteria:

• Blood glucose criteria must be met
• On a stable dose of metformin as defined by the protocol
• Body mass index (BMI) in the range 22-45

Exclusion Criteria:

• Type 1 diabetes
• Pregnancy or lactation
• Evidence of serious diabetic complications
• Evidence of serious cardiovascular complications
• Laboratory value abnormalities as defined by the protocol
• Other protocol-defined exclusion criteria may apply