A 71-year-old man was referred because of memory loss. Magnetic resonance imaging showed a pituitary macroadenoma associated with hydrocephalus. Marked hyperprolactinaemia was present. After 2 months of cabergoline therapy, magnetic resonance imaging showed tumour shrinkage with resolution of the hydrocephalus. We report, for the first time, the adequate and rapid clinical response of a macroprolactinoma-induced symptomatic hydrocephalus in an elderly man to a low and once-a-week dose of cabergoline therapy. Medical therapy with this dopamine agonist in this particular patient was so effective that ventriculo-peritoneal shunting could be avoided.