It is critical to establish efficacy for cognitive enhancement with a selective D1 agonist in a schizophrenic disorder with cognitive impairment and without concomitant neuroleptic treatment to provide momentum for these efforts. The more readily reversible cognitive impairment of SPD provides a unique opportunity for this critical study of the D1 hypothesis to pave the way for development for more severe schizophrenic disorders with their inevitable complicating artifacts.