Survival was compared between 135 patients (II) with intracranial tumours (IT) diagnosed with the aid of CT and 170 cases of IT (I) diagnosed in the same department prior to the introduction of CT. Apart from fewer cases of oligodendrogliomata in group II, the distribution into histological types was identical in the two groups. The age and sex distributions were identical. The percentages in the groups (I/II) of operations (85.7/60.7), autopsy (41.1/15.3) and histological determination of the tumour (87.6/58.5) had decreased considerably while employment of chemotherapy had increased (1.8/20.7). On the whole, survival from the time of diagnosis was found to be better in group (II) (p = 0.026). Survival from the onset of the disease was the same (p = 0.47) indicating that CT had resulted in earlier diagnosis but not a generalized improvement in survival in the entire group of tumour patients. Significantly better survival was found for the histologically verified malignant tumours in group II both for the primary tumours (p = 0.001) and for metastases (p = 0.0058). In this group, survival was found to be improved both from the time of diagnosis (p = 0.0001) and from the onset of symptoms (p = 0.015). It appears from the literature that there is a generalized tendency to omit histological verification of IT frequently in cases where CT suggests a hopeless prognosis. Greater advantages as regards survival with CT may probably be obtained with more frequent employment of stereotactic biopsy.