To present a case of cerebral infarction following thoracic herpes zoster presenting as Gerstmann's syndrome. A 61 year old male developed herpes zoster of T 1-2 dermatomes. Four months later he developed a confusional state together with expressive aphasia, dyscalculia, dysgraphia and finger agnosia with no long tract signs. CT scan of head showed recent infarction of this left parietal lobe. He received a five day course of acyclovir 800 mg four times daily and showed slow but steady improvement. Herpes zoster is uncommonly followed by cerebral infarction. Acyclovir may have a role in therapy of this complication.