The purpose of this article is to describe the characteristics of modulation disorders that have been reported with sensory integration dysfunction and provide strategies for supporting positive development and engagement. Although not well understood, scientists are beginning to link structural and chemical imbalances of the brain with responses to sensory input that seem uncharacteristic or disproportionate. Theorists who study sensory dysfunction often refer to these conditions as "modulation disorders" to reflect the inability of the child to regulate both over- and underarousal or emotional responses to sensory input. The sensory systems related to modulation disorders that are addressed in this article are the tactile system, the vestibular system, and the proprioceptive system. (Contains 1 table.)