Two sibs with partial trisomy-5p are reported. Their father is the carrier of a balanced translocation 46,XY,t(4q+;5p-). Twelve cases of partial trisomy-5p--including our two patients--have been reported. The most common abnormalities found were mental retardation, short stature, dolichocephaly, prominent nasal bridge, prognathism, seizures, hypotonia, ear abnormalities, increased ulnar loops on the fingertips, and cryptorchidism in affected males.