Introduction: The reliability and validity of Turkish version of Childhood Asthma Control Test (C-ACT). Purpose: The management of asthma is an important as well as difficult issue of physician's daily practice particularly in busy clinical settings. C-ACT was created to identify asthma control levels in children aged 4-11 years. Our aim was to evaluate the reliability, validity and responsiveness of C-ACT in a Turkish sample of children with asthma. Method: In this multicenter study, 368 children were enrolled. C-ACT was completed every month by parents and patients who were evaluated in 3 visits within 2 month intervals. At each visit, physicians interpret the control level and decided for the treatment step as established in GINA guidelines. Results: The internal consistency reliability of the Turkish version of C-ACT (C-ACT1 to C-ACT5) was found to be 0.82, 0.83, 0.82, 0.82 and 0.80, respectively (reliability statistics, Cronbach's alpha). Test-retest reliability was 0.71. There was significant correlation between C-ACT and physician's assessment of asthma control at visit 1 (r = 0.65, P <0.001). Conclusions: Turkish version of C-ACT is an accurate and reliable tool to evaluate asthma control in children aged 4-11 years. Its widespread use may facilitate appropriate assessment of asthma control and may lead to decrease the number of uncontrolled patients. © Springer Science+Business Media B.V. 2011.