Our findings are based on clinical observations and not on a designed study. However, in our University Hospital area, all children with suspected or verified HC are sent to the same pediatric cardiologist (TT). Therefore, our patients are probably representative of children with HC, at least in East Finland. Although the number of patients was small, the prevalence of VSD in children with HC was so high, that it is improbable that the association between the 2 diseases is due to chance alone. Larger studies are needed to confirm our results and to show if muscular VSDs are typical of all HC cases or of specific subgroups only. We suggest that children with HC should undergo a thorough echocardiographic examination to detect possible muscular VSDs, which are usually readily detected by modern color flow mapping techniques. Importantly, in children with a muscular VSD, the possibility of HC as an underlying pathology should be kept in mind.