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, in lowering overall blood glucose levels when added to glimepiride in people with type 2 diabetes not at target blood glucose levels on a sulfonylurea alone.

Inclusion Criteria:

• Blood glucose criteria must be met
• Previously treated with a sulfonylurea for at least 3 months
• Body mass index (BMI) in the range 22-45

Exclusion Criteria:

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