Haemophilia-Davies et al. period. Of the five patients studied one had a severe degree of haemophilia, in two it was moderate, and in two mild. The mortality rate in the series was 20%, as one patient eventually died of intracranial infection. Carotid angiography was safely performed on seven occasions in four of the patients, human A.H.F. concentrate being used on five occasions and porcine A.H.F. concentrate on two. It is suggested that the administration of these A.H.F. concentrates in sustained and adequate amounts to patients with classical haemophilia who are thought to be suffering from intracranial haemorrhage will possibly make it safe to use the standard techniques in establishing the precise diagnosis, and subsequently to treat a lesion by either conservative or surgical means. We wish to thank our neurosurgical colleagues Mr.