Here, we report two cases with isolated distal 11q rearrangement and multiple congenital anomalies. Thefirst patient is a two-anda-half year old male referred to our genetics clinic due to dysmorphic features and developmental delay including speech delay. Using conventional andmolecular cytogenetic techniques, we demonstrate that he carries a recombinant chromosome with duplication of the 11q23.3q24.2 region resulting from an intrachromosomal insertion in the father. The second patient was originally reported by Partida-Perez, et al. [Partida-Perez et al., 2006] as having a tandem duplication of the 11q23.3 region. We performed array comparative genomic hybridization (aCGH) on this patient in order to map the exact region of the duplication, and demonstrated that the patient actually had a triplication within 11q23.3. We compare the clinical features of our two patients with those previously reported to further delineate the phenotype of isolated distal 11q duplication. Our study also demonstrates the clinical usefulness of whole genome high resolution aCGH analysis as a powerful molecular cytogenetic tool capable of detecting genomic imbalances due to cytogenetically visible but uncertain rearrangements. © 2009 Wiley-Liss, Inc.