The two-syndrome concept postulates two "dimensions of pathology" underlying schizophrenia--a reversible (and potentially neuroleptic-responsive) component and a sometimes progressive and relatively irreversible component associated with the deficit state and poor long-term outcome. Negative symptoms (narrowly defined) appear to be more closely associated with the latter component (the type II syndrome), as also are cognitive impairments, abnormal involuntary movements, and behavioral deterioration. This syndrome is assumed to be more closely related than the type I syndrome of positive symptoms to the structural brain changes inferred from pneumoencephalograms, computed tomography scans, and recent post-mortem studies. However, since both syndromes often occur in the same patient--sometimes at the same point in time--they presumably have the same etiology.