Abstract: In order to study the maturation of neurobehavioral systems involved in affect regulation and behavioral choices during adolescence, we examined brain activity associated with response monitoring and error detection using event-related potentials (ERPs). In a visual flanker test, trials with incorrect responses elicit ERP components including an error-related negativity (ERN) and a later error-positivity (Pe). We examined the amplitude and latency of the ERN and Pe of incorrect responses in 124 children from 7 to 18 years of age. The ERN amplitude in error trials increased with age although this was qualified by a nonlinear change. The quadratic distribution of the ERN indicated an initial drop in amplitude (lowest at age 10 for girls; age 13 for boys) with a subsequent rise through adolescence. The Pe amplitude did not change with age. Results are discussed with respect to continued maturation of the anterior cingulate cortex and possible influences on adolescent behaviors.