This 68-year-old man was impotent and had reduced visual acuity in his left eye; serum prolactin was greatly elevated at 109 000 mU/l, and a 3 cm macroadenoma was shown on MRI. He was commenced on treatment with cabergoline, 0.5 mg twice weekly. His left visual acuity started to improve after just one tablet, and his serum prolactin was close to normal after two tablets. Follow up MRIs over a four year period showed approximately 80% tumour shrinkage.