Background and objective: Visual evoked potential (VEP) is an essential element of the diagnostic process of multiple sclerosis. It proves substantially useful in the diagnosis of clinically silent demyelinization lesions of a visual tract. The purpose of the study is the analysis of VEP in patients with diagnosed clinically isolated syndrome – CIS. Material and methods: The study involved 77 patients with diagnosed CIS at the age range from 17 to 54 years old. VEP was performed both with pattern-reversal checkboard and flesh stimulation. Results: Mean values in both tests, were within normal. Abnormal result of VEP was obtained in 24 patients. P100 values exceeded the normal range in 21 cases (27.27%) in reversal test (in 6 patients bilaterally) and in 12 cases (15.58%) in flesh test (in 5 patients bilateral). Description: Presence of abnormal VEP was observed in 31% of examined cases, including 10 cases of retrobulbar optic neuritis in the past. Our results confirm earlier studies on the frequency of occurrence of abnormal VEP values in an early stage of MS. Further observations shall allow assessment of the function of VEP testing in identification of patients at a high risk of clinically definite multiple sclerosis (CDMS).