Objective: Asthma is a chronic inflammatory disease with reversible airway obstruction. Indoor factors play a role in the emergence of asthma and also have many effects on the control of asthma. In this study, we aimed to evaluate the indoor environmental factors that affect whether the disorder is controlled or not. Material and Methods: Children aged 6-18 years with asthma who had been diagnosed and followed-up by the pediatric allergy and immunology clinic of our hospital were included in the study. Control levels of the patients were determined according to the Global Initiative for Asthma (GINA) asthma control guide. The control levels of the patients and the effects of indoor factors on these levels were evaluated. Results: Two hundred ninety one patients with asthma who were diagnosed with clinical findings and respiratory function test were included in the study. According to GINA criteria, 55% of the patients were found to have controlled (n=160) and 45% of the patients uncontrolled (n=131) asthma. Eosinophil counts, number of rooms at home, and the number of older brothers and/or sisters were found to be significantly different between the controlled and uncontrolled groups. Median [interquartile range (IQR)] eosinophil count was 200/mm3 in the controlled group and 200/mm3 in the uncontrolled group (p=0.040). Median (IQR) number of rooms was 4 in the controlled group and 3 (p<0.001) in the uncontrolled group. Median (IQR) number of older brothers or sisters was 1 in the controlled group and 1 (p=0.013) in the uncontrolled group. conclusion: The numbers of eosinophils, rooms and older brothers or sisters were found to be significantly different between patients with controlled asthma and patients with uncontrolled asthma. Other risk factors (gender, atopy, obesity, urban or rural lifestyle) were found not to affect the control of asthma