The authors describe 5 cases of pleural mesothelioma in a rural population of Macedonia, Greece. This population had been covered by an X-ray study over a 3-year period to detect pleural calcifications compatible with asbestos exposure. The study revealed a 24.2% prevalence of pleural plaques among the inhabitants aged over 40 years of 7 rural villages. High contents of asbestos (chrysotile and tremolite)--up to 90% by volume--were found in the material that was used for whitewashing the houses up to 1935. Even now, environmental concentrations of 0.01 fibres/ml were recorded in the houses. The prevalence of pleural mesothelioma in this rural population is high compared to the general population. A possible explanation of the phenomenon may be a cumulative environmental exposure to asbestos which, even though presumably within the acceptable limits for occupational exposure, lasted over a much longer time period, in terms of both daily exposure and total duration.