Angiostrongylus cantonensis is the most common cause of eosinophilic meningitis worldwide. Human infection occurs after ingestion of the worms in raw snails or fish that serve as intermediate hosts. Two outbreaks of central nervous system infection with A. cantonensis occurred in Kaoshiung, Taiwan, during 1998 and 1999 among Thai laborers who ate raw snails. A detailed clinical studies of 17 of these patients was conducted, including study of 13 patients who underwent magnetic resonance imaging (MRI) scans of the brain. The MRI scans revealed high signal intensities over the globus pallidus and cerebral peduncle on T1-weighted imaging, leptomeningeal enhancement, ventriculomegaly, and punctate areas of abnormal enhancement within the cerebral and cerebellar hemisphere on gadolinium-enhancing T1 imaging, and a hyperintense signal on T2-weighted images. There was a significant correlation between severity of headache, cerebrospinal fluid (CSF) pleocytosis, and CSF and blood eosinophilia with MRI signal intensity in T1-weighted imaging (P < 0.05). Eosinophilic meningitis produced by A. cantonensis needs to added to the list of causes of hyperintense basal ganglia lesions found on T1-weighted MRI scans in tropical countries.