Partial deletion of 4p (Wolf syndrome) is reported in two cases resulting from paternal balanced t(4;8)(p163;p231). One of them was diagnosed prenatally and aborted. Autopsy revealed dysmorphic face, and malformed heart and kidneys. The other case, the mentally retarded sister, had no clinical signs of internal malformations, only slightly dysmorphic appearance. We concluded that loss of the terminal segment of 4p(4p163) seems sufficient to produce the clinical entity of Wolf syndrome, and partial trisomy of the short arm of chromosome 8 did not mask the 4p- phenotype. Segregation analysis showed risk figures of about 15% for a malformed child comparable to previously given figures concerning the outcome of autosomal reciprocal translocations.