Objective: There is some evidence that insufficient effort may be common in schizophrenia, posing significant threats to the validity of neuropsychological test results. Low effort may account for a significant proportion of variance in neuropsychological test scores and the generalized cognitive deficit that characterizes the disorder. The current study evaluated the role of effort in neuropsychological test results in schizophrenia using an embedded effort measure, the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) Effort Index (EI). Method: Participants were 347 patients meeting DSM-IV-TR criteria for schizophrenia or schizoaffective disorder. Patients received a battery of neuropsychological tests, including: (1) Wechsler Test of Adult Reading (WTAR), (2) Wechsler Abbreviated Scale of Intelligence (WASI), and (3) RBANS, as well as instruments designed to measure functional outcome, symptoms, and premorbid adjustment. Results: Sixty-four schizophrenia patients (18.4%) failed the EI. Patients who failed had lower full-scale, verbal, and performance IQ, as well as poorer performance on RBANS domains not included in the EI (immediate memory, language), with the exception of visuospatial/construction. Patients who failed also had poorer community-based functional outcome, greater severity of negative symptoms, and poorer premorbid adjustment in childhood and adolescence. Conclusion(s): Poor effort in schizophrenia occurs in a significant minority of patients who appear to have a more severe form of the illness with poor premorbid development, higher levels of negative symptoms, and poorer functional outcomes. Poor effort, which is likely the result of apathy and motivational processes characteristic of the disease, may therefore be an important consideration in the neuropsychological evaluation of schizophrenia.