OBJECTIVE: Asthma is known as a chronic inflammatory lung disease which has also systemic features. Insulin-like growth factor I (IGF-I) plays a role for asthma pathogenesis. Controversially, IGF-binding protein 3 (IGFBP3) blocks asthma development. That is why IGF-I and IGFBP3 are targeted for future therapeutic treatments of asthma. We aimed to investigate serum level of IGF-I and IGFBP3 in patients with asthma. This study was performed in 27 asthma and 23 healthy individuals. Serum levels of IGF-I and IGFBP3 were measured by human ELISA assay kits. Serum levels of IGF-I and IGFBP3 were significanlty higher in the asthma group than the control group. Significant negative correlation was found between IGF-I and asthma control test (ACT) puan, O-2 saturation, Forced Expiratory Volume in 1 second/ Forced Vital Capacity (FEV1/FVC), Forced Expiratory Flow 25 second/75 second (FEF2575) (%). Significant positive correlation was found between IGFBP3 and IGF-I, systolic blood pressure. Significant negative correlation was found between IGF-I and FEV1 (ml).