We report a child in whom we observed markedly increased genome-wide spontaneous chromosomal breakage in both leucocytes and fibroblasts associated with severe growth retardation, radial aplasia, leucopenia, mild hydrocephalus and an unusual trichodystrophy. Exposure to DNA cross-linking agents diepoxybutane, mitomycin-C and mustine hydrochloride in this case did not result in the increased chromosome breakage seen in Fanconi anaemia. It may be that this child has a defect in postreplicative DNA repair interacting with the protein components deficient in FA.