Descriptions of epilepsy in the literature have been written mainly by men working in institutions who had access only to institutionalized patients. Consequently, reports on epilepsy are based almost exclusively on deteriorated, incarcerated patients. Since most writers had no opportunity of observing non-deteriorated, extramural patients with epilepsy these were not included in their studies. Their inclusion, however, is important because there are good reasons for believing that deteriorated patients constitute only a small part of the number of persons with epilepsy.In this study the age of onset of 368 adult non-deteriorated patients with epilepsy was determined and compared with similar data for institutional deteriorated patients.The trends observed were as follows:1. Fewer non-deteriorated patients have the onset before five years of age.2. Fewer non-deteriorated patients have the onset before 10 years of age.3. More non-deteriorated patients have the onset after 20 years of age.4. More non-deteriorated patients have the onset after 40 years of age.It is concluded that deteriorated patients with epilepsy differ from the non-deteriorated ones in that there is a tendency to later onset in the non-deteriorated patients.Abstract Teaser