We report a family in which Wolf-Hirschhorn syndrome in two children with partial monosomy of the short arm of chromosome 4 is the result of unbalanced segregation of a reciprocal 4;12 translocation in the mother. Studies with the DNA probe G8 show that the translocation breakpoint in this family is distal to the D4S10 locus. Previously reported cases of Wolf-Hirschhorn syndrome have involved the deletion of D4S10. These observations may prove helpful in the search for better genetic markers for Huntington's chorea, which maps close to D4S10.