Objective. Recent data demonstrate that control of asthma is far from optimal worldwide. The aim of this study was to evaluate the level of asthma control in tertiary health services by the use of Asthma Control Test (TM) (ACT) and to assess the factors which might influence the control of the disease. Methods. A total of 2336 patients with asthma were recruited from 28 tertiary hospitals in the study. Asthma severity was classified by the frequency of asthma symptoms, pulmonary function tests, and medication requirements according to asthma guidelines. The level of asthma control was assessed by the Turkish version of ACT and determinants of asthma control were evaluated with medical history, physical examination, patients' and disease characteristics. Results. Due to missing data, 1188 subjects' records were evaluated. Nearly half of the patients (51.5%) were found to be "controlled" (ACT >= 20) and 48.5% was defined as "uncontrolled" (ACT < 20). The ratio of uncontrolled asthmatic patients was significantly higher in severe asthmatics than in mild and moderate asthmatics (p < .01). Female sex, education below secondary level, forced expiratory volume in one second (FEV1) value <80%, peak expiratory flow (PEF) value <80%, hospitalization/emergency department visits in the last year, and systemic steroid use were found to be significantly associated with inadequate control (p < .01). Conclusions. This study demonstrated that asthma control was still inadequate in the tertiary level although overall control was better than previous reports in Turkey. Patients with severe asthma were more likely to have uncontrolled disease; worse asthma control was also associated with increased hospitalizations and emergency care admissions.