Sixty-six patients were assessed clinically, psychologically and physiologically before operation, at six weeks and at a mean of 16 months following stereotactic limbic leucotomy. Seventy-three per cent were clinically improved at six weeks and 76 per cent at 16 months. In obsessional neurosis, 89 per cent of patients showed definite clinical improvement at 16 months; in chronic anxiety, 66 per cent were improved; in depression, 78 per cent; and in the small number of schizophrenics treated the improvement rate was over 80 per cent. Self-assessment and observer-assessment questionnaires and scales measuring Depression, Anxiety, Neuroticism, Hysterical symptoms and Obsessional symptoms and traits all showed highly significant reductions of mean scores at 16 months. There was no fall-off in intelligence, and adverse effects were minimal. Limbic leucotomy, with its enhanced accuracy and safety, compares very favourably with similarly assessed, more extensive ‘free-hand’ procedures, and in obsessional neurosis and chronic anxiety the results are superior.