A karyotype with six de novo autosomal abnormalities in chromosomes 2,4,9,10,12, and 13 was identified in a 7-year-old boy with mental retardation and other minor malformations. The G- and C-banding techniques revealed an equilibrated translocation between autosomes 2 and 4 and between autosomes 9 and 13. One chromosome 10 has lost genetic material from its short arms, probably because of an interstitial deletion. An unidentified chromosomal fragment has become inserted in the long arms of an autosome 12. The G bands demonstrate that genetic material inserted in the autosome 12 is not the genetic material deleted from the autosome 10. The propositus presents clinical features similar to the reported cases with 10p- syndrome. Nevertheless it is not possible to establish the influence of the genetic material inserted in autosome 12 on the propositus' phenotype.