AbstractWe report on a 16‐year‐old girl with a multiple congenital anomalies/mental retardation condition, in which a 1.7 Mb tandem duplication of chromosome region 16p13.3 was detected by array‐CGH. Mental retardation was moderate (IQ 45), with very limited speech. She had tall stature with relative microcephaly. Clinical manifestations included distinctive facial appearance with deep set eyes, narrow palpebral fissures, wide nasal bridge, long philtrum, rounded nasal tip, thin upper lip, protruding mandible and abnormal auricles, hand and foot anomalies. The causal 16p13.3 duplication is one of the smallest reported so far, and includes the CBP gene, whose haploinsufficiency is responsible for the Rubinstein–Taybi syndrome. By comparing clinical manifestations of our patient with those of patients carrying similar rearrangements, we could infer that 16p13.3 microduplications encompassing the Rubinstein–Taybi region result in a recognizable clinical condition, most likely representing a single gene disorder. © 2008 Wiley‐Liss, Inc.