Partial tetrasomy of chromosome 22 is a rare multiple congenital anomaly syndrome that is more commonly known as cat-eye syndrome (CES). It is caused by the duplication of a 2-million base region of chromosome 22 (22 pter -> q 11·2). The phenotype is extremely variable, and its clinical characteristics include a combination of craniofacial, cardiac, renal, gastrointestinal, and genitourinary defects. We describe a rare occurrence of CES in a Brazilian family. Three siblings were affected''monozygotic twin boys and their younger brother. All 3 were born to healthy nonconsanguineous parents. On examination, all 3 were found to have strabismus, primary telecanthus, bilateral coloboma iridis, and low-set ears with posterior rotation of the pinnae. Partial tetrasomy of chromosome 22 was confirmed by fluorescent in situ hybridization. To our knowledge, this is the first report of such an occurrence in one family. We discuss the genotype and phenotype of CES, with particular reference to inheritance patterns and craniofacial defects.