To determine the effect of Ruboxistaurin on small fiber function.

Inclusion Criteria:

• Patients must have Type 1 or Type 2 diabetes mellitus
• Patients must have bilateral sensorimotor distal peripheral neuropathy attributable to diabetes mellitus
• Patients must have blood glucose control measured as HbA1c=<11%
• Patients must be 18 years of age or older.
• Patients must be able to return to all follow-up visits

Exclusion Criteria:

• Patients must not have symptoms of diabetic peripheral neuropathy that cannot be distinguished from other etiologies
• Patients must not have a neurologic disease or neuropathy from a cause other than diabetes mellitus that would interfere with correct evaluation of symptomatic peripheral neuropathy.
• Patient currently has uncontrolled high blood pressure
• You have other medical problems that your doctor feels would make it unsafe for you to participate in this study such as liver or kidney problems
• You are a woman of childbearing age and unwilling or unable to use effective contraceptive.