We present three patients with Wolf-Hirschhorn syndrome with small cytogenetic deletions of 4p16. One case is a de novo translocation and two cases represent de novo deletions. Using molecular techniques we determined the extent of these deletions and attempted to ascertain parental origin. Case 1 had a deletion of 4p16.3 with a breakpoint proximal to D4S10, case 2 had a larger deletion including D4S62 in 4p16.2, and case 3 had the largest deletion which included D4S240, but not the Raf2 locus in 4p16.1. The parental origin of the deletion in case 3 was paternal; the other two cases were indeterminable. Our results show that these three deletions include the currently proposed Wolf-Hirschhorn syndrome critical region within the most distal 2 Mb of 4p16.3 and offer supportive evidence for continuous terminal deletions.