Both emotional reactivity and categorization have long been studied within the framework of hemispheric asymmetry. However, little attempt has been made to integrate both research areas using any form of neuropsychological research, despite behavioral data suggesting a consistent relationship between affective and categorization processes. The primary goal of the current study was to examine the possibility of a laterally mediated interaction between emotional reactivity and the cognitive process of categorization. Using a split visual fields categorization task combined with affect inducing procedures, we hypothesized that the relationship between state affect and categorization would be dependent on the nature of state affect and on the hemisphere targeted. Results offered support for this hypothesis, showing that state affect related changes in categorization appeared only in the hemisphere commonly associated with both a specific affective state and categorization strategy employed. Findings are discussed in terms of possible evidence for a hemispheric arousal effect underlying the relationship between affect and categorization.