A national survey of caregivers of individuals with fragile X syndrome addressed characteristics of epilepsy and co-occurring conditions. Of the 1,394 individuals (1,090 males and 304 females) with the full mutation, 14% of males and 6% of females reported seizures. Seizures were more often partial, began between ages 4 and 10 years, and were infrequent and easily treated. Similar characteristics and patterns were seen in medical chart review data from a large clinic cohort of patients with fragile X syndrome. National survey data showed that autism was significantly associated with seizures as a co-occurring condition. Although seizures in fragile X syndrome are typically not severe and easily treated with medications, they appear to be associated with developmental-behavioral comorbidity that impacts function.