Williams syndrome (WS) is a genetic disorder associated with impairments of spatial cognition. This has primarily been studied in small-scale space, and rarely in large-scale environments. In order to fully characterise the spatial deficits in WS, and also to address claims that the deletion of LIM-kinase1 (LIMK1) on chromosome 7 is responsible for those deficits, we report an automated large-scale search task for humans that places the participant egocentrically within the search space. Search locations were defined as lights and switches embedded in the floor, and participants attempted to locate a hidden target by pressing the switch at potential locations. We compared individuals with WS to patients with smaller deletions (including LIMK1) in the critical region on chromosome 7. Whilst partial-deletion participants performed efficiently on the task, participants with WS demonstrated inefficient search profiles: their search slopes were steeper and they made significantly more erroneous revisits to previously inspected locations. Our findings indicate that spatial deficits associated with WS also affect large-scale spatial processing and suggest that hemizygous deletion of LIMK1 is not sufficient to account for any of the spatial deficits associated with WS. © 2009 a Pion publication.