Deficits in visual processing are now recognized as a core feature of schizophrenia. In the 1940s, Louis Thurstone developed a series of tests designed to evaluate specific aspects of visual perceptual processing including the Closure Flexibility Test (CFT), which was designed to measure “the ability to hold a configuration in mind despite distraction.” The present study evaluated patients' performance on this task and its relationship to other tests of neuropsychological function, particularly to a measure of sustained visual attention. Thirty-nine patients with schizophrenia or schizoaffective disorder and 40 controls participated. The CFT was administered both in its original form (10min) and also in a briefer form (3min) in which only a portion of stimuli were given. Patients showed highly significant large effect-size deficits on both the original (d =1.6) and brief (d =1.2) CFT. Between-group deficits in performance survived co-variation for IQ. In addition, the CFT score was significantly related to performance on the MATRICS measure of attention/vigilance, the Continuous Performance Test—Identical Pairs version (CPT-IP). This correlation remained significant even after controlling for non-specific intercorrelations among neurocognitive measures. Results confirm the severity of early visual processing deficits in schizophrenia. In addition, the CFT is a brief, easy to administer alphabet-independent, paper-and-pencil test with established psychometric properties that may be useful as an index of the sustained visual attention construct in schizophrenia.