The "IDDM-Sardinia project" started in the beginning '90s and this main objective was, and still is, to clarify the epidemiological aspects of insulin-dependent diabetes mellitus in Sardinia, an island with a high incidence of the disease. Initially, the project included three main aims: 1) to continue monitoring the incidence of the disease and to design maps of geographical distribution of it in the island; 2) to study the pre-diabetes period, by assaying islet-related autoantibodies (ICA, GADA and IA-2icA), and to design models of prediction in a general population from a large cohort of 10,000 schoolchildren, and 3) to investigate the natural history of the disease by monitoring the appearance of islet-related autoantibodies in a cohort of 19,000 newborn. Most recently, new research lines branched from these main topics, and now the project is also investigating other autoimmune diseases, in particular coeliac disease and autoimmune thyroiditis. In this paper we still summarise and discuss the state-of-the-art of the whole project.