OBJECTIVES: The Chronic disease are ones of high prevalence, duration and slow progression, its cure could not be predicted clearly or will never be. In general, are related to lifestyles and population that is older.To determine the direct sanitary cost depending on chronic comorbidity grade (risk) in patients attended in a primary care setting (PC). METHODS: Retrospective multicentre design. Patients over 14 years were included, pertaining at 6 PC teams that demand assistance during year 2008. Main measures: sociodemographics, risk/casuistic/comorbidity, Charlson index (severity) and direct cost models. The chronic comorbidity was classified beginning from Adjusted Clinical Groups. It was obtained the Resources Utilization Bands (RUB) per patient (rank: 1- healthy user to 5- high morbidity). The complexity/comorbidity was grouped in 10 categories (6 expert forum). Fixed/semi fixed cost were considered (functioning: salary, services, purchases) and variable (tests, referrals, drugs). Explanation power calculation: determination coefficient (R2). It was made an ANOVA analysis for the correction (age, sex, comorbidity) of the models (procedure: Bonferroni). SPSSWIN program; p<0.05. RESULTS: A total of 69,653 patients, age-average: 47.6±18.8 years; women: 54.1%; high morbidity: 4.8%; chronic disease: 3.8±2.3 and total cost: €51.3 million (fixed cost: 12.3%). The 35.4% (n=24,670; CI: 34.5-36.3%) showed ≥5 chronic disease. Binary correlations: comorbidity-BUR: 0.716; cost-comorbidity: 0.596; age-comorbidity: 0.429; p<0,001. Osseo-muscular illness (38.1%), mental (31.6%) and cardiovascular (30.4%) were the same frequencies, p<0.001. The unitary average of the cost corrected was of €736.74±€921.97, with comorbidity ranks between: 1=309.62; 5=842.99; 10=€2,354.05, respectively, p<0.001. Predictive model (R2): age=25.7%; age-sex=26.5%; age-sex-comorbidity=60.3%, of the cost. Women showed more comorbidity. CONCLUSIONS: Chronic comorbidity is associated with a sanitary cost increase. The number of comorbidities explains the major part of the cost. Patient knowledge of risk/complexity enable us doing different strategies of preventive/cure intervention. Key Words: comorbidity, cost, resource use, risk.