The observation of constitutional chromosome abnormalities in a one and half year old boy with Wiedemann-Beckwith syndrome (WBS) and hepatoblastoma prompted us to review the currently available literature dealing with this subject. In approximately 500 published cases with complete and incomplete forms of WBS, 42 malignant and 9 benign neoplasms have been described. Malignant tumors, in particular, mainly consisted of nephroblastomas and adrenocortical carcinomas. The patient presented in this paper is the fourth with a hepatoblastoma. The constitutional karyotype was analysed in 84 cases; in 68 of them with banding techniques. Abnormalities have only been detected in 11 patients. A 47;XXY karyotype, an inversion of chromosome 2, a partial duplication of the long arm of chromosome 8 and reciprocal translocations t(11;22) and t(X;1), respectively, have been observed in one case each. Individually differing changes in the remaining six cases led to a common triplication of the region 11p15. This triplication has also been the only abnormality, which has so far been reported in one out of six investigated WBS patients with a tumor. Cytogenetic analysis in our case revealed an interstitial deletion of the short arm of chromosome 11 and a complete pericentric inversion of the chromosome 9 heterochromatin block. The breakpoints of the deletion, del(11) (p11.1p11.2), are located proximal of those (11p15) reported in anomalies of other WBS patients, as well as proximal of those involved in patients with the aniridia/Wilm's tumor complex (11p13-11p14). Inversion of the heterochromatin of chromosome 9 has been recognized as a normal variant, which generally remains without phenotypic effects.(ABSTRACT TRUNCATED AT 250 WORDS)