The observation of partial trisomy for 5q31-5qter and partial monosomy for the same segment in two offspring within the same family is presented. Their normal mother was a balanced carrier of a reciprocal translocation 46,XX,t(5;10) (q31.3;q26). The trisomic female had craniofacial dysplasia, a short neck, clinodactyly of the 5th fingers, a small umbilical hernia, arhinencephalia, cerebellar hypoplasia, atrial septal defect, an accessory spleen, bifid uterus and vagina, hypoplastic ovaries. Potter syndrome with cystic dysplasia of the left kidney and agenesis of the right, urethral atresia, uterus unicornus with utero-urethral fistula, true hermaphroditism with two ovaries and one testicle were found in her stillborn sister. Analysis of the manifestations of monosomy 5q and trisomy 5q in the same family supports a well known fact that the effects of deletions are more pronounced than those of duplications for the same segments.