Carriers of balanced reciprocal translocations may have a (high) risk for producing liveborn children with an unbalanced karyotype. We report a large family in which a translocation between the long arm of chromosome 11 and the short arm of chromosome 13 is segregating in at least five generations. During the course of our study 15 carriers of the balanced translocation were identified and nine cases of partial trisomy of the long arm of chromosome 11 were detected during pre- and postnatal studies. Several of the patients were thoroughly clinically examined and compared with similar published cases.