The intention was to examine critically, which new possibilities, limitations and possible faultiness are to be expected in connexion with applying computerized tomography in the field of brain localization. The examinations concern the correlation of neuropsychological symptoms with focal cerebral lesions. From july 1980 until september 1982 52 persons out of all patients examined in our CT-department during this time, were chosen if they had computertomographically defined focal lesions of one brain hemisphere. They were further examined neurologically, neuropsychologically and by psychological tests using a well-connected plan. The results of 33 cases with circumscribed lesions of the left hemisphere are presented in details. The classification of psychological syndromes followed the most important features. A simple procedure for lesion mapping of CT informations, described by MAZZOCCHI and VIGNOLO (1978) was used for documentation and proof of inclusion of the cortical speech region in the examined brain lesions. Thus it was possible to compare the different patterns of lesions and to form groups of patients with a certain localization of the lesions. The correlations of these lesions with the neuropsychological findings were examined in each group. A high degree of correlation in the sense of the classic conception of brain localization of neuropsychological syndromes was found. The ideocinetic motor aphasia was confirmed as a frequent, well-defined syndrome in cases with lesions of the left lower parietal lobulus.