In this report we present a female newborn with Wiedemann-Beckwith syndrome and duplication 4q/deficiency 18p as the result of an unbalanced paternal 4q/18p translocation: karyotype: 46,XY,t(4;18)(q34.2;p11.32). The different mechanisms resulting in prenatal overgrowth and Wiedemann-Beckwith syndrome phenotype are reviewed. The suggestion is made that contiguous gene duplications/deletions other than those located in the 11p15 region may exist.