We aimed to describe and classify headaches associated with acute stroke, by interviewing patients consecutively admitted to a stroke unit using a validated headache questionnaire and the International Classification of Headache Disorders of the International Headache Society (IHS). One hundred and twenty-four patients (61% ischaemic and 39% haemorrhagic stroke) reported headache. Headaches started mostly on the day of stroke, were more often continuous, pressure-type, bilateral and located in the anterior region, were increased by movement and by cough and lasted for a mean of 3.8 days. Tension-type was the most frequent type of headache. Eleven per cent of headaches could not be classified using the criteria of the IHS. Previous primary headache was documented in 71 patients. The presence of nausea/vomiting due to acute stroke can confound headache classification using the IHS criteria. In up to half of the patients, headache seems to be a reactivation of previous primary headache.