The occurrence of intracranial tumours of diverse histogenesis can be considered occasional. In a careful survey of the literature we have encountered 63 cases of concurrent intracranial tumours: we report five personal observations, too. This review raises the question as to whether the conjoint occurrence of two intracranial tumours is purely coincidental. The statistical analysis of the cases of concurrent intracranial tumours, and the comparison between the frequency found for each different tumour when it is solitary and when it is coincident in a same patient, suggests that a casual connection can be found between tumours of diverse histogenesis.