We report a girl with partial trisomy-8 mosaicism whose clinical findings were those of the Warkany et al. (1962) [17] or trisomy 8 syndrome. A dicentric autosome, dic(8) (qter leads to p21::p21 leads to qter), was found in all abnormal cells and evidence is presented that one centromere was inactive, allowing the dicentric to behave as a monocentric chromosome. The parents had normal karyotypes.