Angiostrongylus cantonensis can induce central nervous system (CNS) injury and cause human eosinophilic meningitis. The CNS has been found to have high expression of interleukin 33 (IL-33), which promotes the pathogenesis of T-helper 2 (Th2)-related disease. Given the predominantly type 2 response induced by A. cantonensis-infected mice and human, it is likely that IL-33 may play a role in aiding this process. We report here that IL-33 protein and ST2L messenger RNA (mRNA) transcripts in the brains were upregulated during A. cantonensis infection and that both splenocytes and brain mononuclear cells became IL-33 responsive and produced interleukin 5 and interleukin 13. Furthermore, administration of IL-33 to A. cantonensis-infected mice enhanced ST2L expression and cytokine production. Interestingly, brain IL-33 protein and ST2L mRNA levels were elevated 14-21 days after infection in BALB/c mice, compared with C57BL/6 mice. Thus, our data indicate that IL-33 produced in the brain may function as an inflammatory mediator in eosinophilic meningitis induced by A. cantonensis.