We describe three cases with abnormal chromosome 9. Patient 1 shows translocation in a homologous chromosome, with a karyotype of 46,XX,t(9;9)(9pter----cen----9pter; 9qter----cen::9q13----9qter), 1qh+. This case has a variety of anomalies, including brain anomalies. Patient 2 shows a partial trisomy 9p with a karyotype of 47,XY,+del(9)(pter----q11:). The patient has the typical clinical features of 9p trisomy syndrome. Patient 3 is unique because of partial 9p tetrasomy mosaicism without phenotypic abnormalities; the karyotype is mos 46,XY/47,XY,+dic(9)(pter----cen----q21::q21----cen----pter).