The aim of this study was to investigate the prevalence and the causative factor of pleural plaques (PP) in 7 neighbouring villages (Monastiraki, Promachi, Megaplatanos, Orma, Polykarpi, Sarakini and Koryphi) located south-west of Aridea in Macedonia, Greece, where many cases of bilateral pleural calcifications were observed in the past. Full size chest radiographs were obtained from 1086 of the 3901 inhabitants over 5 years of age who agreed to participate in the study. The chest radiographs were scrutinized for PP according to International Labour Office criteria. From the total of 1737 inhabitants aged between 5 and 40 years, 268 were examined. None had a positive chest radiograph for PP. Therefore the prevalence of PP was evaluated for the subjects over 40 years of age. The highest prevalence of PP (41.7%) was observed in Monastiraki and none in Koryphi, with the prevalence of the other villages lying in between. Extremely high concentrations of chrysotile and tremolite fibres were found, using polarised light microscopy and X-ray diffraction, in the "white stones" which people use for white-washing their houses prior to 1935. The environmental study revealed 0.01 fibres/ml in a room purposely recently painted with the offending material, and 17.9 ff/ml after scraping. During the 28 months of our study five cases of malignant pleural mesothelioma were diagnosed.