A 3 1/2-year-old boy revealed moderate motor and mental retardation, normal growth, a congenital heart defect and multiple minor dysmorphic signs and anomalies including brachycephaly, orbital hypotelorism, upward slanting palpebral fissures, short and beaked nose, full cheeks, malformed auricles, hypoplastic external genitalia, rocker-bottom feet with prominent heels, and various minor radiologic anomalies of bones. An extra chromosome in his karyotype appeared to represent trisomy of the short arm of chromosome 20 due to a maternally inhherited balanced t(13;20)(p11;q11) translocation.