This paper describes the activity, the sources of informations, methods and results of the "Emilia-Romagna Mesothelioma Registry" (ReM). The Registry started in 1996 and collects all cases of Malignant Mesothelioma (MM) occurring in Emilia-Romagna. 323 new cases (225 males and 98 females) have been detected during the period 1996-2001. Most cases (n = 286) concerned pleura. Other observed localizations were: peritoneum (n = 30), tunica vaginalis testis (n = 4) and pericardium (n = 3). Most of the cases were reported by the Institutes of Pathology and Occupational Health and by the Safety Services (respectively the 62% and the 18%). 87% of all the cases were histologically, 8% TC, 4% radiologically and only 1% clinically confirmed. The regional incidence rate (for 10(5) person-years, age standardized on the 1991 Italian population), has been estimated to be 1.98 in males and 0.88 in females. The highest rates were registered in Piacenza and Reggio Emilia province among men and Reggio Emilia and Ravenna province among women. 72% of cases have been classified as exposed to asbestos (64% occupationally and 8% as domestic/environmentally exposed).