This trial is conducted in Japan. The aim of trial is to investigate the safety of insulin detemir and insulin NPH in children with type 1 diabetes.

Inclusion Criteria:

• Type 1 diabetes for at least one year
• Current treatment of basal-bolus regimen for at least 12 weeks using an intermediate/long-acting human insulin and insulin aspart and/or soluble human insulin
• HbA1C below 11.0%
• Willing to comply with Investigator's instructions
• Able and willing to perform self-monitoring of capillary blood glucose and to take measures in case of hypoglycaemia

Exclusion Criteria:

• Impaired renal function
• Impaired hepatic function
• Known hypoglycaemia unawareness or recurrent major hypoglycaemia (as judged by the Investigator or Sub-Investigator)
• Proliferative retinopathy or maculopathy requiring acute treatment
• Uncontrolled treated/untreated hypertension
• Current treatment with total daily insulin dose of more than 2.00 IU/kg
• Current treatment or expected at the screening to start treatment with systemic corticosteroids