OBJECTIVES: To assess the association between the degree of asthma control and quality of life and to estimate the direct medical costs associated with asthma in real life practice. METHODS: An analytical, cross-sectional study. Study units are primary care users diagnosed of asthma from all over Spain, aged 18 years or older. A multistage cluster sampling has been used for sample selection: 230 participating primary care physicians. The Asthma Control Questionnaire (ACQ) was used to measure asthma control and EQ-5D / EQ-VAS were used to measure quality of life in asthmatic patients. The Spearman rank correlation coefficient was calculated in order to assess the relationship between asthma control and quality of life. Information regarding healthcare resources (hospitalization days, emergency room visits, primary care visits and absenteeism days) during the 12 months prior to the visit was collected, expressed as 2008 euros (according to public tariffs available and inflation rate). RESULTS: Overall, 2159 patients have been evaluated, 42.2% males, mean age 48.5 (95%CI: 47.7 - 49.2). Of these, 37.4% (95%CI: 35.3-39.4) were uncontrolled (score > 1,5) according to ACQ. EuroQol EQ-5D mean score was 0.82 (95%CI: 0.81-0.83). Spearman rank correlation coefficient between ACQ and EQ-5D scores was -0.48879 (p-value <0.0001), and between ACQ and EQ-VAS scores was -0.54942 (p-value <0,0001). Hospitalisations over the last year, resulted in a direct cost of €54.85 per year and patient. In the same way, emergency room visits €271.17, primary care visits €161.31 and absenteeism €322.89. CONCLUSIONS: Better asthma control is associated with better quality of life in asthmatic patients. Poor asthma control leads to a higher use of health care resources and therefore higher direct medical costs in asthmatic patients.