OBJECTIVES: Determine frequency of remissions, relapses, and pharmacoresistance over two decades. Develop a composite measure of seizure control over that time. METHODS: Community-based cohort of children with newly diagnosed epilepsy prospectively followed for up to 21 years with frequent calls and periodic medical record review. Multiple periods of 1-, 2-, 3-, and 5-year remission with subsequent relapses were recorded. Other outcomes included pharmacoresistance (failure of two adequately used drugs), early remission and early pharmacoresistance by 2 years, and complete remission at last contact (CR-LC, 5 years both seizure- and drug-free at last contact). A composite summary of seizure course was created with eight categories ranging from early sustained remission and CR-LC (best) to never achieving a 1-year remission (worst). RESULTS: Five hundred sixteen of 613 participants were followed >/=10 years. An initial 1- 2-, 3-, and 5-year remission occurred, respectively, in 95%, 92%, 89%, and 81%. Relapses followed in 52%, 41%, 29%, and 15%, respectively. Repeated remission after relapse was common. Up to seven 1-year, five 2-year and 3-year, and two 5-year remissions were recorded per participant. Pharmacoresistance at any time, early pharmacoresistance (<2 years), early remission, and CR-LC occurred in 118 (22.9%), 70 (13.6%), 283 (54.8%), and 311 (60.3%). Composite outcomes were early sustained remission with CR-LC (N=172, 33%); later but then sustained remission with CR-LC (N=51, 10%); one (N=61, 12%) or more (N=27, 5%) remission-relapse episodes but then CR-LC; various non-CR-LC outcomes (N=179, 35%); and never achieved 1-year remission (N=26, 5%). These patterns varied across groups defined by epilepsy type and presence of brain insults or neurodisability (p<0.0001). SIGNIFICANCE: The seizure prognosis of pediatric epilepsies is highly variable. Most patients follow complex courses not easily summarized by remission status at the end of a period of follow-up. These complexities may facilitate efforts to understand the impact epilepsy has on young people entering adulthood.