In a population-based study of the incidence of stroke conducted on a broad denominator, it is wise first to carry out a pilot study. To present the results of the pilot phase of the study on stroke incidence in Spain, entitled Iberictus. Population of the study: all cases involving the first episode of acute cerebrovascular disease (stroke or transient ischaemic attack) diagnosed among residents over 17 years of age with their habitual place of abode registered in the areas of study between 15th and 31st October 2005 (total denominator: 1,440,997 inhabitants). prospective, hospital records (basic minimum data set, discharge abstracts) and casualty department registers. Standardised definitions: diagnostic categorisation and pathological, topographical and aetiological classification. Inter-observer agreement analysis among researchers (kappa). A total of 128 cases were identified. Age range, 37-103 years; mean age, 75.7 +/- 13.4 years; 54% were females. In all, 71.1% of the cases were collected by means of a basic minimum data set. There were 91 ischaemic events (29.7% atherothrombotic and 29.7% cardioembolic). Of the 15 haemorrhagic strokes, 40% due to arterial hypertension, six were lobar hemispheric, six were deep basal ganglia, and there were three cerebellar haemorrhages. The incidence of stroke was seen to increase exponentially with age. Inter-observer agreement was good for the classifications that were employed (range of kappa indices, 0.57-0.78). Several problems were detected and corrected in the fieldwork. The Iberictus pilot study yielded data that were consistent with the literature and provided us with the opportunity to detect and correct issues that would hinder us from conducting the main study.