Interstitial deletions of the long arm of chromosome 4 are rare. Different breakpoints are involved. Only one of the patients had a very similar deletion to that of the present case. Both had low birth weight at term; weight, length and head circumference less than the third centile; epicanthic folds; apparently low-set abnormal ears; broad nasal bridge; micrognathia; hypoplastic nails; delayed psychomotor development; and mild mental retardation.