The use of benzodiazepine sensitivity testing in the management of 40 children with intractable seizure disorders was studied. The aetiology and clinical syndromes varied widely with myoclonic, atonic and complex absence seizures predominating. Twenty-five cases had mixed seizure disorders. There was, likewise, a wide range of EEG abnormalities. Seven cases were in non-convulsive status at the time of testing. Diazepam (0.2 mg/kg) was given slowly intravenously and its effect on the EEG was observed. In 21 cases epileptiform activity was abolished. No change was seen in 13 cases and an unusual result was seen in 3. There was a paradoxical response in 3 cases, two of these associated with clinical seizures. Only 1 child in non-convulsive status had a positive result. Following testing, 32 patients went on to long-term oral benzodiazepine treatment. Twenty-one of these patients showed subsequent clinical improvement and 16/21 (76%) had had a positive sensitivity test previously. Eleven of these patients did not improve on long-term treatment. Seven out of the 11 (64%) had had a negative sensitivity test. These results suggest that the benzodiazepine sensitivity test is of value in the long-term management of intractable seizure disorders in childhood, but also emphasise the variability and unpredictability of response to benzodiazepine treatment.