Two cases of parkinsonism after recurrent obstructive hydrocephalus due to idiopathic aqueductal stenosis are reported. In both patients an extrapyramidal syndrome was noted in the absence of contemporaneous evidence of hydrocephalus or shunt failure. One of the patients underwent a shunt operation, but showed no clinical improvement. However, both patients improved after the administration of dopaminergic therapy. The seven previously reported cases of this syndrome were reviewed and it is concluded that the prognosis of the parkinsonism is good, usually with total, or near total, resolution. It is recommended that if a patient with idiopathic aqueduct stenosis develops hydrocephalus or evidence of shunt malfunction in association with acute parkinsonism their shunt should be replaced. If there is no evidence of hydrocephalus or shunt malfunction they should initially be treated with domaminergic medication.