We analyzed the loss of heterozygosity (LOH) for 1p in 18 Wilms tumors using a panel of 11 polymorphic markers. Loss of heterozygosity was identified in 56% of the tumors. The smallest region of overlap was defined for marker D1S247, underlying the 1p35-1p36.1 locus. This is the highest LOH frequency for 1p, or for the well-defined 11p13 and 11p15.5 loci. Based on the fact that tumors of all stages, with both favorable and unfavorable histology, exhibited LOH, we suggest that the 1p35-1p36.1 locus is involved in the etiology of Wilms tumor. (C) Elsevier Science Inc., 2000.