A total of 81 toddlers (24-27 months of age) participated in a biobehavioral investigation of inhibitory control. Maternal report measures of inhibitory control were related to laboratory tasks assessing inhibitory abilities under conditions of conflict, delay, and compliance challenge as well as toddler verbal ability. In addition, unique variance in inhibitory control was explained by task-related changes in brain electrical activity at lateral frontal scalp sites as well as concurrent inhibitory task performance. Implications regarding neural correlates of executive function during early development and a central organizing role of inhibitory processing during toddlerhood are discussed. (Contains 5 tables.)