We report on a newborn infant with a de novo triplication of the distal segment of 5p: 46,XX,trp(5) (pter-->p14::p14-->p15.33::p15.33--> qter) and multiple congenital anomalies consistent with triplication of 5p. Partial triplication was documented by fluorescence in situ hybridization with a cosmid probe specific for 5p15.2 and microdissected probes obtained from "5pter." Partial duplication of the short arm of chromosome 5 is associated with a specific phenotype that appears to be dependent on the chromosomal region duplicated. Duplication of 5p with breakpoints proximal to band p14 is generally associated with distinct craniofacial malformations, cardiac, renal, intestinal, and limb defects, and mental retardation, whereas duplications with breakpoints distal to 5p14 result in a milder phenotype characterized by minor facial anomalies, developmental delay, and seizures. The most proximal breakpoints of the partial triplication in this patient was estimated to be 5p14, suggesting that a more severe phenotype can occur with triplication of the more distal segment.