Background: To describe the clinical features of patients with seizure onset within the first three years of life, and to evaluate risk factors for long-term prognosis. Methods: We selected 266 patients among 3096 individuals consecutively observed at a single Epilepsy Center between 1992 and 2012, and retrospectively analyzed their clinical, EEG, neuro-radiological and genetic characteristics. Results: Mean ages at epilepsy onset and at follow-up were 14.9 months and 29.3 years, respectively. Mean follow-up period 8.2 years. We identified a recognizable etiology in 147 individuals (55.2%), while 76 (28.6%) were Thirty-four patients (27.9%) had a confirmed genetic diagnosis and 12 (9.8%) had a meta-bolic diagnosis. Febrile seizures (p = 0.008), positive family history (p = 0.049), drug resistance (p = 0.048), moderate (p = 0.04) and severe intellectual disability (p = 0.005) were significantly more frequent in patients with seizure onset 0-12 months than in those with onset 13-36 months. Multiple regression analysis demonstrated a link between early age of epilepsy onset and intellectual disability (p = 0.008). No further variables were significantly associated with age at epilepsy onset (for etiology p = 0.095, for drug resistance p = 0.646, and for neuro-radiological findings p = 0.087). Conclusion: Our study demonstrated worse outcome in symptomatic epilepsies in a large and representative sample. We also confirmed that the earlier age at seizure onset, the poorest the epilepsy outcome.