This trial is conducted in Africa, Europe and Oceania. The aim of this trial is to investigate whether insulin detemir combined with insulin aspart compared to NPH insulin combined with insulin aspart could reduce the frequency of hypoglycaemic episodes whilst maintaining the same degree of glycaemic control subjects with type 1 diabetes.

Inclusion Criteria:

• Type 1 diabetes
• Fasting c-peptide below lower limit of normal fasting range
• Duration of type 1 diabetes for at least 12 months
• Current treatment: Basal - bolus regimen for at least 4 months with intermediate or long-acting insulin once, twice or three times daily as basal insulin and 3-4 premeal insulin aspart or lispro injections
• HbA1c maximum 9.0% (using Biorad Variant method)
• Able and willing to perform self-monitoring of blood glucose
• Basal insulin requirement at least 30% of the total daily insulin dose
• BMI (body Mass Index) maximum 35 kg/m^2

Exclusion Criteria:

• Proliferative retinopathy or maculopathy requiring acute treatment
• Total daily insulin dose above 1.4 IU/kg/day
• Known unawareness of hypoglycaemia
• Impaired hepatic function
• Impaired renal function
• Cardiac problems
• Uncontrolled, treated/untreated hypertension
• Known or suspected allergy to trial product or related products