Although various studies have shown that suicidal persons exhibit greater cognitive deficiencies than both normals and other psychiatric patients, researchers as yet have been unable to account for the source(s) of the differences. Some of these differences (e.g., cognitive rigidity and impaired problem solving) hint of possible organic involvement. This study explored the relationship of neuropsychological functioning to suicidal behavior by comparing 20 suicidal and 27 nonsuicidal psychiatric inpatients on several tests of neuropsychological functioning. Although results showed no significant differences between the two groups on most measures, both groups showed evidence of notably high levels of cortical dysfunction relative to test norms. Thirty-five percent of suicidal patients and 44% of nonsuicidal patients scored in the impaired range. Implications of this high frequency of impairment for the treatment of suicidal and nonsuicidal psychiatric patients are discussed.