OBJECTIVES Life expectancy in Italy is constantly increasing (+2,4 years for men and +1,7 years for women from 2001 to 2011) with a consequent effect on health needs and expenditure. Furthermore, on overall population, 21% has one chronic disease, 9,3% two and 8% more than three. The aim of this study is to evaluate the burden of multiple chronic diseases and associated costs in a large community setting of Italian elderly population, starting from Cineca ARNO Observatory. METHODS ARNO Observatory is a comprehensive population-based database which integrates since 1987 administrative data from Local Health Units to monitor health data in the real world. On a population of 10,5 millions of inhabitants we selected a cohort of 2.166.000 (21%) subjects over 65 years. Outpatient drug prescriptions, inpatient hospital discharges, diagnostic, lab tests prescriptions were analyzed during 2012 to evaluate chronic diseases, multiple chronic conditions and illness direct costs. RESULTS From selected cohort, 82,5% has at least one chronic disease and this proportion rises up to 89,6% in over 80s. Hypertension is the most common disease (67%), followed by dyslipidemia (30%) and diabetes (18%). Over 50% of elderly has multiple chronic diseases but the risk of developing concomitant chronic illnesses rises with ages (60% of people aged >=85 have comorbidities). Integration of administrative data led to the evaluation of cost of illness which varies from 2.528€ for hypertension to 13.613€ for Acute Coronary Syndrome; the average cost of patients with 2 or more comorbidities is twice than patients with only one chronic disease. In general, more than a half of cost is due to hospitalization (57%), 27% to drugs and 16% to diagnostic exams (16%). CONCLUSIONS Analyses of real world data represent an effective tool for the evaluation of elderly population diseases and can be a valid instrument to support clinical governance.