We report clinical, cytogenetic, and comparative genomic hybridization findings for three siblings with an unbalanced 4q;16q translocation, minor malformations, and cognitive abnormalities, including childhood apraxia of speech, a rare, severe motor speech disorder. Breakpoint findings indicate that in addition to possible contributions from duplicated genes on chromosome 16, haploinsufficiency of one or more of 11 genes deleted in the telomeric region of the long arm of chromosome 4 is the likely cause of the speech disorder, the associated impairments in cognition and language, and the dysmorphic features. The present findings are the first to document childhood apraxia of speech in a multiplex family using contemporary speech measures. We suggest that genotype-phenotype studies of childhood apraxia of speech occurring in complex neurodevelopmental disorders can elucidate the pathophysiology of this disorder. © 2008 Wiley-Liss, Inc.