Among all unrelated patients, for first time we found a novel and heterozygous non-sense putative mutation (a G→T heterozygote transition at nucleotide 14742) in the exon 5 of TBX5 gene, in two patients (1 and 3 months old infants) with atrial septal defects (ASD) and large ventricular septal defects. Here, TBX5 is linked to atrial septal defect.