This prospective, non-randomized, non-controlled, interventional study will determine whether the Roche automated bolus caclulator (ABC) reduces post-meal hyperglycemia better than the competitor's ABC without causing significant hypoglycemia.

Inclusion Criteria:

• Subjects >/= 18 years at screening
• Type 1 diabetics currently using an insulin pump for management of their diabetes and have been on a pump for at least at least 6 months prior to the screening visit
• Subjects have to use a fast acting analog insulin
• HbA1c = 9% (measured with DCA 2000)
• Willing to perform periods of intensive blood glucose (BG) monitoring for up to 21 days prior to the study (~10 tests per day) with skipped meals and testmeals
• Willing to use the 3 different bolus calculators during the course of the study
• Willing to undergo planned hyperglycemia
• Willing to perform high frequency BG monitoring (> 20 / day) during the experiment

Exclusion Criteria:

• Type 2 Diabetes
• Manifest severe late complications of diabetes (e.g. severe macro- or microangiopathy, severe neuropathy, severe retinopathy and/or severe nephropathy)
• Current addiction to alcohol or substances of abuse
• Pregnant or lactating women
• Any known life-threatening disease