Background: Giant prolactinomas are rare tumors representing only 0.5-4.4% of pituitary adenomas, and 2-3% of prolactin secreting tumors. Clinical presentation is similar than smaller prolactinomas. However, due to the large adenoma size (≥4 cm), the normalization of prolactin levels and reduction of the tumor volume becomes a significant therapeutic challenge and multimodal treatment might be necessary. Methods: Comparative, cross-sectional, observational, retrolective cohort, from January 1988 to December 2017. We included all patients with hyperprolactinemia, those with non-tumoral etiologies were eliminated. Our final sample consisted of 327 patients with prolactinomas. We classified them according to tumor diameter using magnetic resonance imaging (MRI), in microprolactinomas (<10mm), macroprolactinomas (≥10 mm) and giant prolactinomas with a diameter of ≥4 cm, together with prolactin level > 1000 ng/dl, and no concomitant growth hormone (GH) or adrenocorticotropic hormone (ACTH) secretion. Results: 244 (74.6%) cases had a microprolactinoma, 72 (22%) had a macroprolactinoma, and 11 patients (3.4%) met the selection criteria for giant prolactinomas (9 males). The most common presenting features included headache, impaired vision, and erectile dysfunction. The main hormone deficiency found in men was testosterone (77.8%), followed by Thyroid-stimulating Hormone (TSH) (63%). Mean prolactin (PRL) at presentation was 2,000 ng/mL (IC 95% 1727 - 4374). All patients were treated with dopamine agonists (DA), and only 3 (27%) patients required surgery. Tumor shrinkage for giant prolactinomas with dopamine agonist was 63% on average. All patients had improved visual field defects. Since patients responded well to DA, none required further treatment modalities. Conclusions: Giant prolactinomas are rare tumors with a male predominance. Dopamine agonists are a useful therapeutic strategy, and good response is seen with a similar average dose to those used in smaller prolactinomas. None of our patients required further medical treatment modalities although surgical debulking sometimes is necessary.