The paper discusses the role of electrophysiological testing (pattern electroretinogram, pattern visual evoked potentials, multifocal visual evoked potentials) in the early diagnosis of the optic nerve and retinal dysfunction secondary to pituitary tumors. Microadenomas and macroadenomas may cause dysfunction of retinal ganglio~ cells and their axons, even in the absence of changes in the routine ophthalmic examination, perimetry and optical coherent tomography of the optic disc. The early stage of optic nerve dysfunction may only be detected by pattern visual evoked potentials and/or multifocal visual evoked potentials. Hemifield pattern visual evoked potentials was more often abnormal and sensitive than full-field pattern visual evoked potentials. Additionally, dysfunction of the retinal ganglion cells can also be quantified by pattern electroretinogram. The results of this test have prognostic value relative to postoperative visual acuity. Based on available literature and our experience it seems to be reasonable to perform the electrophysiological tests as a part of diagnosis and monitoring in patients with pituitary tumors. Detecting functional abnormalities at the early stages of the disease may lead to changes in therapeutic approaches and in turn reduce the incidence of irreversible optic nerve damage. pituitary adenoma, PERD, PVEP, mfVEP, optic nerve dysfunction.