Intellectual impairments are commonly found in schizophrenia and may precede onset of illness. Thought disorder (TD), also a key characteristic, entailing bizarre and idiosyncratic speech may be associated with early intellectual impairments. Schizophrenia and schizoaffective patients (n = 149) were characterized as having preserved, deteriorated, or compromised intellect using premorbid and current IQ estimates. TD and severity of cognitive symptom were ascertained using the Gorham's Proverbs Test, PANSS and SAPS. Significant relations were found between performance-based (Gorham's Bizarreness score) and clinically-rated PANSS (r = 0.51) and SAPS (r = 0.50) symptomatology. Group contrasts on bizarreness revealed higher severity TD (p < 0.01) in compromised as compared with deteriorated and preserved groups. Groups did not differ significantly on PANSS and SAPS related TD ratings. Findings support the etiological significance of TD with respect to clinical course. Importantly, groups were distinguished by performance-based but not on clinical ratings of TD, suggesting a more reliable, trait-related, index of mental change relevant to the course of schizophrenia.