Schizophrenia is a common disorder in which strong genetic predisposition is combined with environmental factors. Despite the widely recognized developmental nature of the disease, symptoms do not emerge until late adolescence. Current therapeutic approaches are therefore employed too late, as brain alterations may have been present earlier than symptom onset. Here I review the developmental trajectory of the cortical circuits responsible for excitation–inhibition balance, which are at the center of current pathophysiological views, and propose that oxidative stress in cortical interneurons may be a final common pathway by which several different etiological factors can yield the cortical dysfunction characteristic of schizophrenia. If this scenario is correct, redox modulators may be beneficial for the disease. It is critical that the developmental trajectories of the factors yielding oxidative stress are taken into account for those approaches to succeed.