We reviewed records of 85 patients with juvenile myoclonic epilepsy (JME) for significant asymmetries in clinical seizures or the EEG. We noted asymmetries in 26 of 85 patients (30.6%). Only 2 patients had both clinical and EEG asymmetries; 12 had clinical asymmetries and 12 had EEG asymmetries exclusively. Analysis of patients with and without asymmetries showed no statistically significant differences in comparisons of sex, age at seizure onset, family history of epilepsy, seizure type, or response to treatment. The delay in diagnosis was greater in JME patients with asymmetries (9.5 years) than in JME patients with no asymmetries (7.5 years), but this difference was not statistically significant. Fourteen of the 26 patients with asymmetries (53.8%) were initially misdiagnosed as having partial seizures. Asymmetries in JME patients are not only common, but are also a frequent cause of misdiagnosis.