The purpose of this study was to investigate the therapeutic prognosis of adult patients with epilepsy during long-term follow-up. The subjects of the present study were 286 epileptic patients seen by the author at the Department of Neuro-Psychiatry, Okayama University Hospital and Tsuyama Sekizen Hospital. All patients had been on therapy for more than five years. The age, onset of seizure and period of treatment of these patients were in order 35.1±11.5 y.o. (mean±SD), 15.9±10.2 y.o. (mean±SD), and 12.4±4.9 years (mean±SD). As classified by the criteria of the International League Against Epilepsy, the present study consisted of cases with; Partial Seizures 167 (58.4%) Primary Ceneralized Seizures 115 (40.2%) Secondary Generalized Seizures 4 (1.4%) The clinical course over the past three years was used as the period to determine the therapeutic prognosis. To describe the therapeutic prognosis, four categories were created taking types and frequency of seizures into consideration; i.e., "seizure-free", "mild", "moderate", and "severe". Results were: 1) "Seizure-free" 99 (34.6%), "mild" 91 (31.8%), "moderate" 54 (18.9%), and "severe" 42(14.7%). 2) In 187 patients, seizures were not abolished. In 89 cases (47.6%) change of seizure type occurred under treatment. The facts elucidated were; a) Partial seizures were resistent even to continued therapeutic efforts. b) Tonic-clonic general convulsions in primary generalized seizures and partial seizure with secondarily generalized responded well to therapy, disappearing promptly and permanently. c) "Abortive-minor seizure" occurred under treatment. d) The change from primary generalized seizures to partial seizures was seen in several cases. 3) Multidimensional comparisons regarding factors which may influence therapeutic prognosis were conducted. In "seizure-free" and "severe" cases, factors which showed statistically significant differences were as follows; In "seizure-free" cases, the first of each following pair showed the better prognosis; a) Seizure types: Primary generalized seizures and partial seizures. b) Etiology: "hereditary" and "residual". c) Etiology: "cryptogenic" and "residual". d) Duration prior to therapy: "within 3 years" and "over 3 years". In "severe" cases, the first of each following pair showed the poorer prognosis; a) Seizure types: partial seizures and primary generalized seizures. b) Etiology: "residual" and "cryptogenic". c) Sexual differences: women and men. 4) Psychiatric problems were observed in 143 cases (50.0%). These patients had a poor prognosis. Patients with partial seizures had more psychiatric problems than patients with primary generalized seizures.