A child with aniridia, multiple anomalies, severe failure to thrive, and severe psychomotor retardation is shown to have a syndrome similar to, though more severe than, other patients with overlapping deletions of the short arm of chromosome 11 (Pediatrics 64:604, 1978). Her deletion (46,XX,del [11p] [pter yields p14::p11.3 yields qter]) was derived from her mother, who has a chromosome 11 shift (46,XX,der [11] [pter yields p14::p11.3 yields q22::p14 yields p11.3::q22 yields qter]). The significance of del (11p) in the aniridia-Wilms' tumor association is discussed, and the del (11p) basis for aniridia is compared with other genetic bases for aniridia.