A de novo interstitial deletion of part of the long arm of chromosome 10 [de(10)(q11.2q21)] was identified by GTG (G‐bands by trypsin using Giemsa) banding in a 9‐year‐old girl with mental retardation and minor anomalies. Only one other case of a similar deletion has been reported [Ray et al, 1980] and the phenotypic findings of the two cases are compared.