The 4q-Syndrome: Here we report four cases of interstitial and terminal deletions of the long arm of chromosome 4. Case 1 is a 16 month old boy with del(4)(q12q21) who has soft dysmorphic features, tetralogy of Fallot, and severe developmental delay. Case 2 is a male infant with the same deletion and congenital cardiomyopathy. He suffered severe birth asphyxia and died at the age of 6 months. His father was found to have a complex chromosome 4 rearrangement. Case 3 is a female infant with del(4)(q33) who died of aspiration pneumonia. She was mildly dysmorphic and presented with heart failure and hypercalcaemia. Case 4 is a 8 month old girl who has del(4)(q33) and Pierre-Robin sequence. So far about 70 patients with microscopically visible deletions of chromosome 4q have been described. Although they vary in their phenotypes, they have several features in common. We suggest to use the term 4q-syndrome for all macrodeletions of the long arm of chromosome 4.