Background: Multiple sclerosis (MS) begins with an acute clinical attack (clinically isolated syndrome) in approximately 85% of patients. The conversion rate from clinically isolated syndrome to multiple sclerosis has been documented at 30% to 82% in previous studies. When an individual presents for evaluation after a single episode of inflammation of the CNS, several decisions regarding follow-up in subsequent years need to be made, including that of whether or not to start a therapy. There is, therefore, an emerging need to identify the predictive factors that anticipate conversion from CIS to MS. Methods: This paper presents a single-center prospective longitudinal study aimed at identification of the most powerful independent predictors for conversion from CIS to MS, utilizing the 2010 McDonald MS criteria and focusing on selected demographic, clinical, radiographical (magnetic resonance imaging - MRI), cerebrospinal fluid (predominantly oligoclonal bands - OCB) and electrophysiological parameters (multimodal sensory and motor-evoked potentials - EP). Two independent outcomes meeting MS criteria are evaluated: development of second clinical relapse (clinically definite multiple sclerosis) and progression in magnetic resonance imaging (based on new MRI T2 brain and/or spinal cord lesions). CIS patients were followed clinically and MRI was repeated at one and two years within the course of a follow-up period of at least 24 months (median 27, range 24-36 months). Results: Of the 64 CIS patients enrolled who completed at least a 2-year follow-up period (42 women and 22 men, median age 36.5, range 22-66 years), 45 (70.3%) (29 women and 16 men, median age 38; range 22-66 years) fulfilled the 2010 McDonald criteria for MS by dissemination in space (DIS) and time (DIT) over the follow-up period. Twenty-nine CIS patients converted to MS through a clinically symptomatic attack, and 16 CIS patients developed new T2 lesions on MRI, while 19 patients without progression remained stable as CIS. Confirmed among potential predictors for the conversion of CIS patients to MS were increased (>10) baseline MRI T2-hyperintense lesions (odds ratio (OR) 3.107, p = 0.046), OCB positivity (OR 5.958, p = 0.003) and subclinical EP abnormality (OR 14.400, p = 0.003). Multivariate statistical models (logistic regression and Cox proportional hazards regression models) confirmed these parameters as independent predictors of high sensitivity (84%) and acceptable specificity (63%). Conclusion: In addition to accepted predictors for the conversion of CIS to MS (i.e. baseline MRI T2 lesion load and OCB positivity), already implemented in current diagnostic criteria for MS, this study demonstrates, in addition, the high predictive value of subclinical multimodal evoked potential abnormalities.