We report the case of a man of aged 27 years who presented with obstru
ctive hydrocephalus caused by a colloid cyst of the third ventricle. H
e was found to have an additional and larger colloid cyst lying adjace
nt to it, but within the lateral ventricle. The contents of the two cy
sts were of different consistency. We have been able to find only one
previous report of more than one colloid cyst occurring in the same pa
tient and none where one of the cysts lay within the lateral ventricle
.