Prolactin-secreting adenomas (prolactinomas) are the most common secreting adenomas of the pituitary. Microprolactinomas (diameter <10 mm) are frequently diagnosed in women, whereas macroprolactinomas (maximum diameter ≥10 mm) are generally seen in men. Most macroprolactinomas measure between 10 and 40 mm. Giant prolactinomas, measuring >40 mm, are rare, accounting for only 1–5% of all prolactinomas. Although generally benign, giant prolactinomas are aggressive and invasive, extending into the suprasellar region and also involving the cavernous sinuses. The optic chiasm is frequently involved, which leads to visual damage, and patients occasionally suffer from ophthalmoplegia. Long-term (usually lifetime) therapy with high-dose dopamine agonists (cabergoline or bromocriptine), together with pituitary surgery in some cases and radiotherapy if required, can achieve biochemical remission, tumor control, and clinical improvement in most patients.