Methods for standardized classification of epileptic seizures are impo
rtant for both clinical practice and epidemiologic research. In this s
tudy, we developed a strategy for standardized classification using a
semistructured telephone interview and operational diagnostic criteria
. We interviewed 1,957 adults with epilepsy ascertained from voluntary
organizations. To confirm and expand the seizure history, we also int
erviewed a first-degree relative for 67% of subjects and obtained medi
cal records for 59%. Three lay reviewers used all available informatio
n to classify seizures. To assess reliability, each reviewer classifie
d a sample of subjects assigned to the others. In addition, an expert
physician classified a sample of subjects assigned to two of the revie
wers. Agreement was ''moderate-substantial'' for generalized-onset sei
zures, both for the comparisons between pairs of lay reviewers and for
the neurologist versus lay reviewers. Agreement was 'substantial-almo
st perfect' for partial-onset seizures, both for pairs of lay reviewer
s and for the neurologist versus lay reviewers. These results suggest
that seizures can be reliably classified by lay reviewers, using opera
tional criteria applied to symptoms ascertained in a semistructured te
lephone interview.