A 14-year-old girl with skin rash and acute interstitial pneumonitis is presented. She had been taking carbamazepine for two months. Withdrawal of carbamazepine resulted in a prompt improvement of the clinical picture and a normalization of lung function tests. A hypersensitivity reaction to carbamazepine is suggested and the importance of a skin rash as first sign of a generalized reaction is stressed. Lymphocyte-stimulation-tests with carbamazepine were strongly positive in the patient and not in healthy persons nor in patients taking carbamazepine without adverse effects.