By statistical analysis of 47 cases with Holt-Qram syndrome(HOS), we found that the severity of the upper limb abnormalities and cardiac defects in HOS varied significantly with different individuals. The variations of appearance were related with the types and positions of mutatons of TBX5 gene which could damage the gene function and cause HOS. It is suggested that the genetic heterogeneity in HOS may be caused by the mutations of different genes.