There have been anecdotal reports of raised glutamic acid decarboxylase (GAD) autoantibodies in patients with refractory epilepsy. We measured serum GAD autoantibodies in 105 patients with idiopathic or symptomatic epilepsy. There was no significant difference in the absolute titre of GAD autoantibody between patients with controlled and uncontrolled epilepsy. However, four female patients with uncontrolled epilepsy had levels that were over three times above the highest detected in the seizure-free group, three of whom also tested positive for pancreatic islet cell antibodies. Larger scale studies, perhaps comparing different epilepsy syndromes, are required to determine the exact clinical role of GAD autoantibodies in epilepsy.