A detailed questionnaire has been devised for diagnosis of seizure type. It is suitable for administration by trained interviewers, either directly or by telephone. A comparison of physician-based and questionnaire-based diagnoses showed almost perfect agreement in classification of patients into those with seizures of either generalized or focal origin. Substantial to almost-perfect agreement was reached in diagnosis of patients with most individual seizure types. Disagreement in differentiation between simple and complex partial seizures (CPS) probably reflects the limitations of the clinical method rather than of the questionnaire itself. The questionnaire should be of value in large-scaled clinical and epidemiologic studies.