A 5-year-old boy with Silver-Russell-like phenotype and developmental delay was found to have a ring chromosome 15. The same r(15) was found in his slightly mentally retarded mother with mild dysmorphism. Analysis of the literature showed 34 families with direct vertical transmission of a ring autosome. In 30 of these families abnormal chromosomes were inherited from the mothers; both maternal and paternal transmission was shown in different generations of one family; and only in 3 families ring chromosomes were inherited from the fathers. The possible explanations of preponderance of maternal transmission are briefly discussed.