Hemispherectomy in man (ablation of the cortex, the underlying white matter and nucleus lentiformis) was performed first by Dandy (1928, 1933), later by Gardner (1939) and a few others, on adult patients suffering from large infiltrating tumours of the subdominant hemisphere, with one exception (Zollinger, 1935). It was carried out by McKenzie (1939) apparently on a patient suffering from infantile hemiplegia with epilepsy. Krynauw (1950a, b) began systematic work of this nature on cases of infantile hemiplegia with epilepsy and personality disturbances. Apart from its therapeutic value, in carefully selected infantile hemiplegics, in the hope of lessening or curing epilepsy, and exerting a beneficial influence on behaviour and further mental development, the comparatively small loss of functions after removal of one hemisphere is most remarkable.