INTRODUCTION: Few data are available on the epidemiology of interstitial lung diseases (ILDs), especially after the current classification of idiopathic interstitial pneumonias. The aim of this study is to provide data on the epidemiology of ILDs in Greece, under the ATS/ERS international consensus.METHODS: Departments of Pneumonology were contacted and asked to complete a questionnaire for every case of ILD that was alive on 2004 as well as for every new case from 1st January 2004 to 31st December 2004. Questions on the patients' demographic data, the exact diagnosis and the procedures used to establish the diagnosis were included. Centers covering about 60% of the Greek population have been analyzed.RESULTS: A total of 967 cases have been registered. The estimated prevalence of ILDs is 17.3 cases per 100,000 inhabitants. The estimated annual incidence of ILDs is 4.63 new cases per 100,000 inhabitants. The most frequent disease is sarcoidosis (34.1%), followed in decreasing order by idiopathic pulmonary fibrosis (19.5%), ILD associated with collagen vascular diseases (12.4%), cryptogenic organizing pneumonia (5.3%), histiocytosis (3.8%), and hypersensitivity pneumonitis (2.6%). Unclassified ILD or not otherwise specified accounted for the 8.5% of prevalent cases.CONCLUSIONS: These data suggest that sarcoidosis and idiopathic pulmonary fibrosis are the most frequent ILDs in our population. In comparison with the few previous reports, interesting dissimilarities have been observed.