Two cases of de novo duplication of the distal part of the long arm of chromosome 14 are reported. In one case, the partial trisomy of 14q is due to translocation of a segment (14q24 to 14qter) at the end of the satellite stalk of chromosome 14. The clinical picture is very severe. In the second case, a tandem duplication in 14 (q23----q32) is present with only minor malformations and mild mental retardation.