Considering the importance of the TGF-β signaling pathway for normal lung function and especially its roles in inflammation and tissue remodeling, key features of asthma pathology, it can be assumed that these molecules may harbor mutations in asthmatics. The aim of this study was to analyze the SMAD4 gene in patients with asthma. Analysis has encompassed exons 10, 11, 12 and 13 encoding the carboxy-terminal (MH2) domain of the SMAD4 protein, where mutations most frequently occur. The study included 50 patients (20 men and 30 women) with asthma aged between 17 and 73 years (average age 45.2±15.6 years). Polymerase chain reaction (PCR) was used to amplify exons 10, 11, 12 and 13 of the SMAD4 gene and the obtained PCR products were subjected to direct DNA sequencing. No nucleotide changes were found in any of the analyzed exons in either of the subjects. Based on the results of this study, it seems that mutations in the carboxy-terminal (MH2) domain of the SMAD4 are not present in asthmatic patients. Future research should be directed at the analysis of the complete gene, including regulatory elements, in order to resolve the exact role of SMAD4 in asthma.