Nonepileptic seizures (NES) must be distinguished from epilepsy to avoid the adverse effects of unnecessary antiepileptic drugs and to initiate appropriate psychiatric treatment. A higher frequency of prior sexual abuse has been suspected in NES, although no prospective controlled study has compared patients with NES and epilepsy. A series of patients with conversion disorder presenting as epilepsy and 140 patients with complex partial epilepsy (CPE) without evidence of conversion were selected from a series of consecutive admissions to a comprehensive epilepsy center. The groups did not differ with respect to age, years of education, race, or marital status, but the percentage of women was greater in the conversion NES group (73.2%) than in the CPE control group (50.7%; p < 0.002). The frequency of a history of sexual or physical abuse was greater in the NES group (32.4%) than in the CPE controls (8.6%; p < 0.000). Severity of sexual but not physical abuse was significantly greater in the NES group relative to controls (p < 0.05). There was a trend for a closer relationship of the perpetrator of sexual abuse to the victim among the NES patients compared with CPE controls (p < 0.1). These results support the impression that childhood abuse is more common among patients with conversion NES than with epilepsy, and suggests that in some cases childhood abuse may be a contributory pathogenetic factor.