Objective: Although the genetic origin of Idiopathic/Genetic Generalized Epilepsy (IGE) is hardly disputed, only a minority of patients show Mendelian inheritance. We here questioned if clinical characteristics like long-term outcome and treatment response differ between patients with sporadic and familial IGE. Methods: In a near-population based cohort of IGE patients, clinical characteristics, treatment response and family history of 443 IGE patients were analyzed. In patients reporting at least one close relative (max. 3rd grade) with suspected IGE, we designed pedigrees and estimated possible inheritance. Results: We found 121 patients (27.3%) with a positive family history of IGE, 322 (72.7%) patients had sporadic IGE. Pedigrees suggesting possible autosomal-dominant pattern of inheritance were found in 52 (11.7%) patients. Clinical characteristics, seizure frequency, surrogate markers for social outcome, psychiatric and somatic comorbidity, seizure type, EEG features, treatment response to lamotrigine, levetiracetam or valproic acid and risk of treatment resistance were similar in all groups. Conclusion: Familial and sporadic IGE patients do not differ in terms of clinical phenotype and treatment response.