The association of Wilms' tumor with aniridia (the WAGR complex) in children with 11p13 chromosomal abnormalities has been established, but the paucity of molecular probes in 11p13 has hampered identification of the responsible genes. Two new anonymous DNA segments have been identified that map to the WAGR region of 11p13. Both DNA probes identify a cytologically undetectable deletion associated with a balanced chromosome translocation inherited by a patient with familial aniridia, but not Wilms' tumor. The same two DNA segments are also included in the distal p13-p14.1 deletion of another patient, who has aniridia, Wilms' tumor, and hypogonadism, but they are not included in the p12-p13 deletion of a third patient, who does not have aniridia but has had a Wilms' tumor. The discovery of this aniridia deletion and these two DNA segments that physically separate the Wilms' tumor and aniridia loci should facilitate identification of the genes in the WAGR locus, beginning with the aniridia gene.