Two groups of patients were studied with a battery of tests. Both groups were matched as to sex, age, intelligence, and clinical status. One group was leucotomized and the other not. The leucotomized group showed a significant loss on Kohs' Blocks, the Bender Gestalt test and Paired Associates. The conclusions drawn were that the patients who are most improved clinically after leucotomy are those who are most impaired on the tests and that the changes on the test are dependent on conative changes in the patient, not on a reduction in capacity.