INTRODUCTION: It is estimated that at least 30 to 40% of asthma attacks in adults are related to respiratory infections with viruses. The majority of asthma-related viruses include respiratory syncytial virus (RSV), rhinovirus, and parainfluenza. Inflammatory cytokines are supposed to play a vital role in causing inflammation of the respiratory tract as regulators of proliferation, chemotaxis, and activation of inflammatory cells. OBJECTIVES: The aim of this study is to assess the role of Granulocyte Macrophage-Colony Stimulating Factor (GMCSF) in asthmatic airway hyper-responsiveness associated with RSV infections. MATERIALS AND METHODS: Forty five asthmatic cases and 45 healthy individuals were studied in a cross-sectional design. All asthmatics underwent symptom score assessment.GMCSF concentrations in sputum and RSV-IgM/IgG in serum samples were measured for all participants by Enzyme Linked Immuno-Sorbent Assay (ELISA). RESULTS: The GM-CSF concentration level was significantly higher in asthmatics (270.27+/- 194.87pg/mL) especially among moderate and severe disease with mean concentration of 197.33+/-98.47 and 521.08+/- 310.04 respectively, compared to healthy controls (22.20+/-21.27 pg/ mL) (p =0.0001). The sputum level of GM-CSF in asthmatics is highly significant associated with positive anti-RSV IgG sera which represents 35/45(77.8%) with mean GM-CSF concentration of (276.99+/- 86.42) compared with controls at about 31/45 (68.9%) with GM-CSF mean concentration of (22.84+/-23.47). On the other hand, positive anti-RSV IgM in asthma cases was 8 out of 45(17.8 %) with GM-CSF mean concentration of (307.25+/- 306.65). Furthermore, GM-CSF sputum level was significantly correlated with eosinophil count especially in moderate and severe asthma. CONCLUSIONS: This study revealed that GM-CSF level is associated with eosinophilia and indicates asthma severity that might be evident during RSV infection .The distinctive GM-CSF features observed in the sputum from asthmatics with RSV may be useful as a diagnostic methods to help match patients with antibody therapy.