This is a research study of a study drug known as LY041001 or human insulin inhalation powder (HIIP). HIIP is a powder form of insulin made to be inhaled through the mouth and into the lungs using a special handheld device.

Inclusion Criteria:

• You are at least 18 years old.
• You have had type 1 diabetes for at least 2 years.
• You are injecting insulin lispro (Humalog), an insulin lispro mixture (Humalog Mixture), regular human insulin mixture (Humulin mixture) before meals using a syringe or injection pen, not an insulin pump.
• If you are female and could become pregnant, you test negative for pregnancy based on blood test at the beginning of the study, do not intend to become pregnant, and agree to use a form of birth control approved by the investigator during the study.
• You have not smoked for at least 1 year, and you agree not to smoke or use smokeless tobacco during the study.

Exclusion Criteria:

• You have used an experimental drug during the last 30 days or have ever taken part in a study of any type of inhaled insulin.
• You have a history of asthma or allergies.
• You have a chronic cough.
• You have had a kidney transplant, are on dialysis, or have poor kidney function.
• You have a history of chest pain, heart attack, or you have a heart condition that limits your physical activity due to discomfort.