The role of categorization in visual search was studied in 3 colour search experiments where the target was or was not linearly separable from the distractors. The linear separability effect refers to the difficulty of searching for a target that falls between the distractors in CIE colour space (Bauer, Jolicoeur, & Cowan, 1996b). Observers performed nonlinearly separable searches where the target fell between the two types of distractors in CIE colour space. When the target and distractors fell within the same category, search was difficult. When they fell within three distinct categories, response times and search slopes were significantly reduced. The results suggest that categorical information, when available, facilitates search, reducing the linear separability effect.