A case of choroid plexus papilloma of the III ventricle associated wit
h hydrocephalus in an 1-month-old boy is reported. The tumor was remov
ed after placement of a ventriculoperitoneal shunt; however, the histo
logically mainly benign tumor grew very rapidly. The cause of this rap
id growth may have been a drop in the intraventricular pressure after
the shunting procedure.