Cri Du Chat syndrome results from the loss or deletion of a significant portion of the genetic material from the short arm of one of the pair of number five chromosomes. It is a relatively rare genetic condition with an estimated incidence of between around 1:25000 to 1:50000 births. There are more children being diagnosed now that genetic testing is carried out more frequently and is more accurate. The incidence appears to be the same in most countries, ethnic groups and regions. To date, there is no single environmental factor implicated in the incidence of this syndrome. The most distinctive characteristic, and the one for which the syndrome was originally named in 1963 by geneticist Jerome Lejeune, is the distinctive high-pitched, monotone, cat-like cry. “Cri du Chat” is French for “cat’s cry”. The cry is thought to be the result of structural abnormality and low muscle tone. Although the voice will naturally lower as the child grows, the characteristic high pitch often persists into adulthood. In addition to the cry, there are a number of distinguishing characteristics present in infancy which aid in recognition of the syndrome. Not every child will have every feature. Those only mildly affected may have very few or they may be less obvious. More information about the syndrome is available at www.criduchat.asn.au.